WORKS  OF  PROF.  HEINRICH  RIES 

PUBLISHED   BY 

JOHN  WILEY   &  SONS 


Building:  Stones  and  Clay  Products 

A  Handbook  for  Architects.  8vo,  xiii+415 
pages,  59  plates,  including  full-page  half-tones 
and  maps,  20  figures  in  the  text.  Cloth,  $3.00  net 

Clays:  Their  Occurrence,  Properties  and  Uses 

With  Especial  Reference  to  Those  of  the  United 
States.  Second  Edition,  Revised.  8vo,  xix  + 
554  pages,  112  figures,  44  plates.  Cloth,  $5.00 
net. 

By  RIES  AND  LEIGHTON 

History    of    the    Clay-working:    Industry    in    the 
United  States 

By  Prof.  Heinrich  Ries  and  Henry  Leighton, 
Assistant  Economic  Geologist,  New  York  Geo- 
logical Survey.  8vo,  viii  +  270  pages,  illustrated. 
Cloth,  $2.50  net. 


PUBLISHED    BY 

THE   MACMILLAN    CO. 


Economic  Geology,  with  special  reference  to  the 
United  States. 

8vo,   xxxii  +  589  pages,   237   figures,   56  plates. 
$3.50  net. 


BUILDING  STONES 
AND  CLAY-PRODUCTS 

A   HANDBOOK    FOR    ARCHITECTS 


BY 

HEINRICH    RIES,    PH.D. 

\    I 

Professor  of  Economic  Geology  in  Cornell  University;  Fellow,  Geological  Society 

of  America;  Member,  American  Institute  of  Mining  Engineers,  Canadian 

Mining  Institute,  American  Society  for  Testing  Materials, 

American  Ceramic  Society,  English  Ceramic  Society 


FIRST  EDITION 
FIRST   THOUSAND 


NEW  YORK 

JOHN    WILEY    &    SONS 

LONDON:   CHAPMAN  &  HALL,   LIMITED 

1912 


COPYRIGHT,  1912, 

BY 
HEINRICH  RIES 


Stanbopc  ]press 

F.    H.GILSON    COMPANY 
BOSTON,  U.S.A. 


PREFACE 


THAT  at  least  an  elementary  knowledge  of  the  subject  of  build- 
ing stones  and  clay  products  is  of  importance  to  the  architect 
few  people  will  deny,  since  familiarity  with  their  properties, 
durability,  and,  in  the  case  of  clay  products,  their  methods  of 
manufacture  will  enable  him  to  select  and  use  these  materials 
more  intelligently. 

At  the  same  time,  the  preparation  of  an  elementary  work  on 
the  subject  is  not  free  from  difficulties,  for  the  reason  that  most 
architects  have  but  a  limited  knowledge  of  geology  and  ceramic 
technology.  The  author  has,  therefore,  attempted  to  state  facts 
and  explanations  as  simply  as  possible,  and  as  a  further  aid  in 
this  direction  has  included  a  glossary  at  the  end  of  the  book. 

The  general  arrangement  of  the  book  follows  the  course  of 
lectures  given  each  year  to  the  students  in  the  College  of  Archi- 
tecture of  Cornell  University,  and  it  has  been  the  encouraging 
reception  which  these  received  that  has  led  the  author  to  give 
them  to  the  public. 

The  work  is  not  intended  as  an  exhaustive  treatise,  but,  in  stead, 
aims  to  give  simply  the  fundamentally  important  facts.  It  is 
therefore,  beyond  the  scope  of  the  book  to  take  up  any  but 
the  more  important  occurrences  of  building  stone,  and  those 
who  desire  detailed  information  on  this  point  will  consult  our 
standard  American  work,  "  Stones  for  Building  and  Decora- 
tion "  by  G.  P.  Merrill. 

Since  the  architect  often  desires  to  know  how  extensively 
and  for  what  purposes  the  different  building  stones  have  been 
used,  an  attempt  has  been  made  to  give  a  list  of  structures  in 
which  the  more  important  ones  at  least  have  been  placed. 

The  author  wishes  to  acknowledge  here  assistance  and  advice 
received  from  many  persons  in  the  preparation  of  the  work 

iii 


263614 


IV  PREFACE 

including  Mr.  E.  C.  Stover,  Trenton  Potteries  Co.,  Trenton,  N.  J. ; 
Mr.  W.  H.  Gorsline,  Rochester,  N.  Y.;  Prof.  C.  W.  Parmalee, 
Rutgers  College,  New  Brunswick,  N.  J. 

Acknowledgments  for  cuts  or  photos  loaned  are  made  under 
the  respective  illustrations. 

HEINRICH  RIES. 

CORNELL  UNIVERSITY,  ITHACA,  N.  Y. 
June,  1912. 


CONTENTS. 


PAGE 

PREFACE iii 

CONTENTS v 

LIST  OF  PLATES ,  jd 

LIST  OF  FIGURES xv 

INDEX 401 

PART   I. 
BUILDING  STONES. 

CHAPTER  I. 
ROCK  MINERALS  AND  ROCKS 3 

Introduction,  3;  Rock-forming  minerals,  5;  Physical  properties,  5; 
Hardness,  6;  Cleavage,  6;  Lustre,  6;  Form,  6;  Quartz,  7;  Feldspars,  7; 
Orthoclase,  7;  Plagioclase  feldspar,  7;  Micas,  8;  Amphibole,  9;  Horn- 
blende, 9;  Tremolite,  9;  Pyroxene,  9;  Calcite,  10;  Aragonite,  10; 
Dolomite,  10;  Gypsum,  10;  Serpentine,  n;  Talc  or  steatite,  n; 
Olivine,  n;  Garnet,  n;  Chlorite,  n;  Pyrite  or  iron  pyrite,  12;  Mag- 
netite, 12;  Limonite,  12;  Rocks,  12;  Igneous  rocks,  12;  Granite,  18; 
Pegmatite,  18;  Syenite,  23;  Diorite,  23;  Gabbro,  23;  Peridotite,  23; 
Pyroxenite,  23;  Granite  porphyry,  23;  Syenite  porphyry,  23;  Diorite 
porphyry,  24;  Felsite,  24;  Basalt,  24;  Stratified  rocks,  24;  Sandstone, 
29;  Conglomerate,  29;  Shale,  29;  Limestone,  29;  Chalk,  30;  Calcareous 
tufa,  30;  Travertine,  30;  Onyx,  30;  Coquina,  30;  Dolomite,  30;  Meta- 
morphic  rocks,  30;  Quartzite,  30;  Slate,  30;  Phyllite,  31;  Marble,  31; 
Ophicalcite,  31;  Gneiss,  31;  Schist,  31;  Structural  features  affecting 
quarrying,  31;  Bedding,  32;  Joints,  32. 

CHAPTER  II. 

PROPERTIES  OF  BUILDING  STONE 36 

Texture,  36;  Hardness,  36;  Color,  37;  Variation  in  color,  38;  Change 
of  color,  38;  Polish,  40;  Specific  gravity  and  porosity,  40;  Absorption, 
44;  Quarry  water,  44;  Crushing  strength,  44;  Transverse  strength,  51; 
Frost  resistance,  54;  Fire  resistance,  55;  Expansion  and  contraction  of 
building  stones,  69;  Abrasive  resistance,  70;  Discoloration,  73;  Effect  of 
sulphurous  acid  gas  and  dilute  sulphuric  acid,  74;  Effect  of  carbonic 
acid  gas,  74;  Chemical  composition  of  building  stones,  75;  Weathering 
and  decay  of  building  stones,  75;  Disintegration,  76;  Temperature 


VI  CONTENTS 

PAGE 

changes,  or  heat  and  cold,  76;  Expansion  caused  by  freezing,  79;  Abra- 
sive action,  80;  Plant  action,  80;  Careless  methods  of  extraction  and 
working,  80;  Decomposition,  81;  Sulphurous  and  sulphuric  acids,  85; 
Hardening  of  stone  on  exposure,  85;  Life  of  a  building  stone,  86;  Sap,  87; 
Literature  on  building  stones,  87;  General  works,  87;  Serials,  88;  Special 
papers,  88. 

CHAPTER  III. 

IGNEOUS  ROCKS  (CHIEFLY  GRANITES)  AND  GNEISSES 93 

Characteristics  of  granites,  94;  Elasticity,  94;  Flexibility,  94;  Expan- 
sibility, 95;  Porosity,  95;  Fire  resistance,  95;  Chemical  composition,  95; 
Classification,  95;  Structure  of  granites,  96;  Sheets  or  beds,  96;  Knots, 
96;  Inclusions,  99;  Dikes,  99;  Black  granites,  99;  Tests  of  granite,  99; 
Uses  of  granite,  105 ;  Distribution  of  igneous  rocks  (chiefly  granites)  and 
gneisses  in  the  United  States,  105;  Eastern  belt,  105;  Maine,  106;  North 
Jay,  106;  Crotch  Island,  106;  Hallowell,  106;  Vinalhaven  and  Hurri- 
cane Islands,  109;  Red  Beach,  109;  Addison,  109;  Jonesboro,  no; 
Blue  Hill,  no;  Brookville,  no;  Dix  Island,  no;  Clark's  Island,  no; 
Machias,  no;  Pleasant  River,  no;  Stonington,  no;  Classification  of 
Maine  granites,  no;  New  Hampshire,  in;  Concord,  in;  Milford,  112; 
Conway,  112;  Auburn,  112;  Troy,  112;  Fitzwilliam,  112;  Mascoma 
granite,  near  Enfield,  113;  Classification  of  New  Hampshire  granites, 
113;  Vermont,  116;  Hardwick,  116;  Barre,  116;  Bethel,  116;  Wood- 
bury,  119;  Windsor,  119;  Massachusetts,  120;  Milford,  120;  Rock- 
port,  120;  Chester,  125;  Quincy,  125;  Classification  of  Massachusetts 
granites,  125;  Rhode  Island,  128;  Westerly,  128;  Connecticut,  128; 
Branfprd  township,  131;  Greenwich,  131;  Waterford  township,  131; 
Millstone,  131;  Groton,  132;  Market  price  of  granites,  136;  New  York, 
137;  New  Jersey,  137;  Pomp  ton  pink  granite,  138;  Dover  light  gray 
granite  gneiss,  138;  Cranberry  Lake  white  granite  gneiss,  138;  German 
Valley  gray  granite,  138;  Trap  rock,  138;  Maryland,  138;  Granites,  141; 
Port  Deposit,  141;  Ellicott  City,  141;  Guilford,  141;  Woodstock,  141; 
Frenchtown  area,  142;  Gneisses,  142;  Virginia,  142;  Petersburg  area, 
142;  Richmond  area,  142;  Fredericksburg  area,  145;  Other  localities, 
145;  North  Carolina,  145;  Even  granular  granites,  146;  Coastal  plain, 
146;  Piedmont  plateau  region,  146;  Greystone,  149;  Raleigh,  149; 
Wise,  149;  Rowan  County,  149;  Mount  Airy,  149;  Porphyritic  granites, 
149;  Miscellaneous  rocks,  150;  South  Carolina,  150;  Heath  Springs,  153; 
Columbia,  153;  Georgia,  154;  Elberton-Ogelsby-Lexington  area,  154; 
Lithonia-Conyers-Lawrenceville  area,  154;  Fairburn-Newman-Green- 
ville  area,  154;  Stone  Mountain  area,  155;  Sparta  area,  155;  Alabama, 
155;  Wisconsin-Minnesota  area,  155;  Wisconsin,  155;  Montello,  155; 
Berlin,  156;  Warren,  156;  Waupaca,  156;  Wausau,  157;  Amberg,  157; 
Minnesota,  157;  Southwestern  area,  158;  Missouri,  158;  Graniteville, 
158;  Knob  Lick,  158;  Arkansas,  159;  Oklahoma,  159;  Wichita  Moun- 
tains, 159;  Arbuckle  Mountains,  159;  Texas,  160;  Cordilleran  area,  160; 
Montana,  160;  Colorado,  160;  California,  161;  Rocklin,  161;  Ray- 
mond, 161;  Riverside  County,  161;  Oregon,  161. 


CONTENTS  Vii 

CHAPTER  IV.  PAGE 

SANDSTONES 162 

Texture,  162;  Hardness,  162;  Color,  163;  Absorption,  163;  Crushing 
strength,  163;  Weathering  qualities,  165;  Fire  resistance,  165;  Varieties 
of  sandstone,  165;  Arkose,  165;  Bluestone,  165;  Brownstone,  165;  Cal- 
careous sandstone,  165;  Ferruginous  sandstone,  166;  Flagstone,  166; 
Freestone,  166;  Graywacke,  166;  Quartzite,  166;  Distribution  of  sand- 
stones and  quartzites,  166;  New  England  States,  166;  Eastern  Atlantic 
States,  167;  New  York,  167;  Medina  sandstone,  167;  Potsdam  sand- 
stone, 167;  Warsaw  blue  stone,  168;  Hudson  River  bluestone,  168; 
New  Jersey,  168;  Pennsylvania,  169;  Maryland,  169;  Virginia,  170; 
West  Virginia,  170;  Alabama,  170;  Central  States,  170;  Ohio,  170;  In- 
diana, 173;  Illinois,  174;  Michigan,  174;  Wisconsin,  174;  Minnesota,  175; 
Missouri,  176;  Arkansas,  176;  Western  States,  176;  Montana,  176; 
Colorado,  176;  Washington,  177;  California,  177. 

CHAPTER  V. 

LIMESTONES  AND  MARBLES 178 

Limestones  and  dolomites,  178;  Color,  178;  Hardness,  178;  Texture, 
178;  Absorption,  181;  Weathering  qualities,  181;  Crushing  strength,  181; 
Fire  resistance,  181;  Tests  of  limestone,  181;  Chemical  composition, 
183;  Varieties  of  limestone  and  dolomite,  183;  Chalk,  183;  Coquina, 
183;  Dolomite,  183;  Fossiliferous  limestone,  183;  Hydraulic  limestone, 
183;  Lithographic  limestone,  183;  Magnesian  or  dolomitic  limestone, 
184;  Marble,  184;  Oolitic  limestone,  184;  Travertine,  calcareous  tufa, 
or  calc  sinter,  184;  Distribution  of  limestone  in  the  United  States,  184; 
New  York,  189;  New  Jersey,  189;  Pennsylvania,  189;  Maryland,  190; 
Virginia,  190;  West  Virginia,  190;  Alabama,  190;  Florida,  191;  Illinois, 
191;  Indiana,  191;  Kentucky,  192;  Ohio,  192;  Wisconsin,  192;  Minne- 
sota, 195;  Missouri,  196;  Iowa,  196;  Kansas,  196;  Texas,  197;  Cor- 
dilleran  region,  197;  Marbles,  197;  Mineral  composition,  197;  Color, 
198;  Texture,  198;  Weathering  qualities,  201;  Absorption,  201; 
Crushing  and  transverse  strength,  201;  Uses  of  marbles,  201;  Dis- 
tribution of  marbles  in  the  United  States,  202;  Vermont,  202;  Light 
marbles,  207;  Dark  marbles,  213;  Ornamental  or  fancy  marbles,  213; 
Champlain  marbles,  214;  Massachusetts,  215;  Connecticut,  215;  New 
York,  215;  Pennsylvania,  216;  Maryland,  216;  Virginia,  217;  North 
Carolina,  217;  Tennessee,  218;  Georgia,  218;  Alabama,  223;  Mis- 
souri, 223;  Colorado,  223;  Arizona,  223;  California,  224. 

CHAPTER  VI. 

SLATE 225 

Classification  of  slate,  225;  Properties  of  slate,  229;  Sonorousness,  229; 
Cleavability,  229;  Cross-fracture,  229;  Character  of  cleavage  surface, 
229;  Lime,  229;  Color  and  discoloration,  229;  Presence  of  clay,  229; 
Presence  of  marcasite,  230;  Strength,  230;  Toughness  or  elasticity,  230; 
Density  or  specific  gravity,  230;  Abrasive  resistance,  230;  Corrodibility, 
230;  Electrical  resistance,  230;  Tests  of  slates,  233;  Price  of  slate,  235; 
Quarrying,  236;  Distribution  of  slate  in  the  United  States,  236;  Maine, 


Viii  CONTENTS 

PAGE 

237>  Vermont,  237;  Sea  green  slate,  237;  Unfading  green  slate,  237; 
Purple  and  variegated,  237;  New  York,  238;  New  Jersey,  238;  Penn- 
sylvania, 238;  Maryland,  241;  West  Virginia,  241-;  Virginia,  241; 
Georgia,  241;  Arkansas,  241;  California,  242. 

CHAPTER  VII. 

SERPENTINE 243 

Distribution  of  serpentine  in  the  United  States,  243;  Massachusetts, 
244;  Vermont,  244;  New  York,  244;  New  Jersey,  244;  Pennsylvania, 
244;  Maryland,  249;  Georgia,  249;  California,  249;  Washington,  249; 
Onyx  marbles,  249. 

PART   II. 
CLAY  PRODUCTS. 

CHAPTER   VIII. 

PROPERTIES  OF  CLAY 253 

Physical  properties,  253;  Plasticity,  253;  Shrinkage,  254;  Tensile 
strength,  255;  Fusibility,  255;  Chemical  properties,  256;  Analyses  of 
clay,  258. 

CHAPTER  IX. 

BUILDING  BRICK 259 

Kinds  of  brick,  259;  Raw  materials  used  for  building  brick,  263; 
Common  brick,  263;  Pressed  brick,  263;  Enameled  brick,  264;  Methods 
of  brick  manufacture,  264;  Preparation,  264;  Molding,  265;  Soft  mud 
process,  265;  Stiff  mud  process,  269;  Dry  press  and  semi-dry  press 
process,  275;  Re-pressing,  276;  Drying,  276;  Burning,  279;  Compari- 
son of  brick  made  by  different  processes,  283;  Testing  of  brick,  284; 
Crushing  test,  284;  Transverse  test,  294;  Absorption  test,  296;  Rate  of 
absorption,  300;  Permeability,  301;  Relation  between  crushing  strength, 
transverse  strength,  and  absorption,  302 ;  Fire  tests,  302;  Coefficient  of 
expansion,  305;  Frost  test,  305;  Proposed  standard  specifications  for 
building  brick,  307;  Selection  of  samples,  307;  Transverse  test,  307; 
Compression  test,  308;  Absorption  test,  308;  Freezing  and  thawing  tests, 
308;  Requirements,  309;  Specific  gravity,  309;  Efflorescence  or  scum 
on  bricks,  312;  Testing  bricks  for  scumming  power,  313;  Requisite 
qualities  of  brick,  314;  Common  brick,  314;  Pressed  brick,  314; 
Enameled  brick,  317. 

CHAPTER  X. 

ARCHITECTURAL  TERRA  COTTA : 320 

Definition,  320;  Raw  materials,  320;  Method  of  manufacture,  320; 
Properties  of  terra  cotta,  324;  Testing  terra  cotta,  324;  Terra  cotta 
scum,  328;  Fire-resisting  properties,  328. 

CHAPTER  XI. 

HOLLOW- WARE  FOR  STRUCTURAL  WORK  AND  FIREPROOFING 333 

Types  of  hollow-ware,  333;  Raw  materials  and  manufacture,  333; 
Fireproofing,  334;  Furring  blocks,  338;  Hollow  block  and  brick,  338; 
Tests  of  hollow  blocks,  340;  Fire  tests,  346. 


CONTENTS  ix 

CHAPTER  XII. 

ROOFING  TILE 349 

Shingle  tile,  349;  Old  Spanish,  Normal,  Mexican,  Mission  or  Roman 
tile,  350;  Modern  Spanish  or  S  tiles,  350;  Interlocking  tile,  351;  Ma- 
terials and  manufacture,  352;  Porosity  of  roofing  tiles,  352;  Requisite 
characters  of  roofing  tile,  359;  Tests  of  roofing  tile,  359;  Miscellaneous 
clay  slabs,  used  for  roofing  purposes,  360;  Special  shapes,  360. 

CHAPTER  XIII. 

WALL  AND  FLOOR  TILE 363 

Manufacture  of  wall  tile,  363;  Properties  of  floor  tile,  365;  Method  of 
manufacture,  366;  Tests  of  wall  tile,  369;  Tests  of  floor  tile,  369. 

CHAPTER  XIV. 

SEWER  PIPE  AND  SANITARY  WARE 372 

Sewer  pipe,  372;  Raw  materials,  372;  Manufacture,  372;  Requisite 
qualities,  374;  Strength,  374;  Durability,  377;  Serviceability,  377; 
Specifications,  377;  Iowa  standard  specifications  for  drain  tile  and  sewer 
pipe,  379;  Absorption  tests,  379;  Bearing  strength,  380;  Computing 
the  Modulus  of  Rupture,  381;  Other  proposed  standard  tests,  382; 
Miscellaneous  tests,  384;  Other  hollow  shapes,  385;  Sewer  blocks,  386; 
Sanitary  ware,  388;  Vitreous  ware,  388;  Solid  porcelain,  388;  Raw 
materials,  388;  Manufacture,  388;  Properties  of  sanitary  ware,  388; 
Glossary,  390. 


LIST   OF   PLATES 


PLATE  PAGE 
I.   A  small  fine-grained  dike  of  dark  diabase  cutting  a  lighter  colored 

syenite 13 

II.   A  volcanic  rock,  trachyte,  showing  porphyritic  texture 15 

III.  Fig.  i.  Moderately  fine-grained  granite,  Hallowell,  Me 19 

Fig.  2.  Very  coarse-grained  granite,  St.  Cloud,  Minn 19 

IV.  Coarse-grained    somewhat    porphyritic    granite    from    Crotch 

Island,  Me 21 

V.   Pegmatite,  showing  coarse-grained  texture 25 

VI.    Fig.  i.  View  in  a  limestone  quarry  showing  the  horizontal  strati- 
fication planes  and  vertical  joint  planes 27 

Fig.  2.  General  view  of  a  limestone  quarry  showing  stratified 

character  of  the  rock 27 

VII.    Biotite  gneiss,  showing  characteristic  banded  structure  of  this 

rock 33 

VIII.    Fig.  i.  Gray  marble,  Gouverneur,  N.  Y.,  showing  contrast  be- 
tween tooled  and  polished  surfaces 41 

Fig.  2.  Gabbro  from  Keesevilte,  N.  Y.,  showing  contrast  between 

tooled  and  polished  surfaces 41 

IX.    Fig.  i.  Photomicrograph  of  a  section  of  granite 45 

Fig.  2.  Photomicrograph  of  a  section  of  diabase 45 

X.    Photomicrograph  of  a  section  of  quartzitic  sandstone 47 

XI.    Fire  tests  on  3-in.  cubes  of  sandstones  from  Pleasantdale,  N.  J.  .  57 

XII.   Fire  tests  on  3-in.  cubes  of  limestone,  Newton,  N.  J 59 

XIII.  Fire  test  of  3-in.  cubes  of  gneiss,  Mt.  Arlington,  N.  J.  . 61 

XIV.  Fire  tests  of  3-in.  cubes  of  sandstone,  Warsaw,  N.  Y 63 

XV.   Fire  tests  of  3-in.  cubes  of  diabase,  Lambertville,  N.  J 65 

XVI.   Results  of  abrasion  tests  with  sand  blast 71 

XVII.   Fig.  i.  Weathering  of  red  sandstone,  Denver,  Col 77 

Fig.  2.  Weathered  sandstone,  second  story  County  Court  House, 

Denver,  Col 77 

XVIII.   Scum  of  soluble  salts,  which  has  caused  surface  disintegration  of 

sandstone 83 

XIX.    Church  in  Mexico  City  constructed  of  volcanic  tuff 91 

XX.   Fig.  i.  Granite  quarry,  Hardwick,  Vt 97 

Fig.  2.  Granite  quarry  at  North  Jay,  Me 97 

XXI.   Map  showing  distribution  of  igneous  rocks  and  gneisses  in  the 

United  States 102 

XXII.    Cleveland  Trust  Company,  Cleveland,  O.,  constructed  of  North 

Jay,  Me.,  granite 107 

XXIII.   Map  of  Vermont  showing  granite  centers  and  prospects 117 

xi 


xii  LIST  OF  PLATES 

PLATE  PAGE 

XXIV.   Map  of  Massachusetts  showing  quarry  centers 121 

XXV.    Fig.  i.  Milford,  Mass.,  granite  showing  speckled  appearance, 
caused  by  biotite  scales  against  lighter  background  of  quartz 

and  feldspar 1 23 

Fig.  2.  Battle  monument  on  Lookout  Mountain,  Chattanooga, 

Tenn.,  constructed  of  Milford  pink  granite 123 

XXVI.   Battle  monument,  West  Point,  N.  Y.,  polished  shaft  of  Branford 

granite,  41  ft.  6  in.  long  and  6  ft.  diameter. 129 

XXVII.   Map  of  Maryland  showing  distribution  of  granite  quarries  and 

granite  and  gneiss  areas 137 

XXVIII.   Fig.  i.  Port  deposit,  Maryland,  gneissic-granite  with  face  cut  at 

right  angles  to  banding 143 

Fig.  2.  Port  Deposit,  Maryland,  gneissic-granite  with  face  cut 

parallel  to  the  banding 143 

XXIX.   Fig.  i.  Leopardite  from  North  Carolina 151 

Fig.  2.  Orbicular  gabbro  from  North  Carolina 151 

XXX.   U.  S.  Post  Office,  Toledo,  O.,  constructed  of  Berea  sandstone ....  171 

XXXI.   Fig.  i .  Limestone  showing  dark  flint  nodules 1 79 

Fig.  2.  Tremolite  in  dolomitic  marble 179 

XXXII.    Map  showing  limestone  areas  of  United  States 186 

XXXIII.  Statue  of  Labor,  cut  in    "Old  Hoosier"   Light  Blue   Bedford 

limestone  for  City  Investment  Building,  New  York  City 193 

XXXIV.  A  decorative  marble  showing  a  brecciated  structure 199 

XXXV.   Interior  of  Harris  County  Court  House,  Houston,  Texas,  showing 

Creole  matched  marble 203 

XXXVI.   Fig.  i.  White  marble,  Vermont 205 

Fig.  2.  Gray  marble,  Vermont 205 

XXXVII.   Fig.  i.  Quarries  in  Travertine  near  Tivoli,  Italy 209 

Fig.  2.  Quarry  of  Vermont  Marble  Company,  Proctor,  Vt 209 

XXXVIII.    Kimball  monument,  Chicago,  111.,  done  in  Vermont  white  marble  211 
XXXIX.    Monolith  of  Georgia  marble,  27  ft.  2  in.  by  4  ft.  4  in.  by  4  ft.  3  in., 

weight  50  tons 219 

XL.    Slabs  of  Alabama  marble  showing  variation  from  pure  white  to 

those  which  are  clouded  and  streaked  with  mica 221 

XLI.   Fig.  i.  Slate  quarry,  Penrhyn,  Pa 227 

Fig.  2.  Splitting  slate 227 

XLII.    Map  showing  distribution  of  slate  in  the  United  States 239 

XLIII.    Serpentine  pedestal,  Charlottesville,  Va 245 

XLIV.    Serpentine  from  Roxbury,  Vt 247 

XLV.   Fig.  i.  Ornamental  dry-pressed  brick 261 

Fig.  2.  Tapestry  brick 261 

XL VI.   Fig.  i.  Common  red  soft-mud  brick 267 

Fig,  2.  A  common  soft-mud  brick 267 

XL VII."  Section  of  stiff-mud  brick  showing  laminations 271 

XL VIII.  '  Dry-press  brick  machine 273 

XLIX.   Fig.  i.  Common  brick  split  by  lime  pebbles 277 

Fig.  2.  Repressed  brick 277 


LIST  OF  PLATES  xiii 

PLATE  PAGE 

L.   Fig.  i.  Setting  brick  for  a  scove  kiln 281 

Fig.  2.  Down-draft  kilns  used  for  burning  sewer  pipe 281 

LI.    Brickotta,  a  style  of  ornamental  brickwork 315 

LII.   Terra  cotta  panel  used  in  construction  of  State  Education  Build- 
ing, Albany,  N.  Y 321 

LIII.  Terra  cotta  panel,  Rice  Hotel,  Houston,  Tex 325 

LIV.   Interior  of  Railway  Exchange  Building,  Chicago,  111 329 

LV.   Flat  arch  of  fireproofing 335 

LVI.   Regular  and  special  shapes  of  Spanish  interlocking  tile 353 

LVII.   Fig.  i.  Interlocking  shingle  tile  showing  obverse  (A)  and  reverse 

(B)side 357 

Fig.  2.  Molding  3o-inch  sewer  pipe  in  pipe  press 357 

LVIII.   Encaustic  tile 367 

LIX.   Sewer  pipe  and  fittings 375 


LIST   OF   FIGURES 


FIG.  PAGE 

1.  Sandstone  broken  by  transverse  strain  caused  by  settling  of  the  building  52 

2.  Effect  of  fire  on  granite  columns,  U.  S.  public  storehouse,  Baltimore.  ...  55 

3.  Map  showing  granite  producing  areas  of  North  Carolina 147 

4.  Diagram  showing  electric  connections  made  in  testing  slate 231 

5.  Diagram  showing  some  patterns  of  slate  that  can  be  cut  on  a  machine ....  235 

6.  Diagram  showing  section  of  slate  rcof  with  starting  and  finishing  courses  236 

7.  Soft-mud  brick  machine 266 

8.  Manufacture  of  brick  by  stiff-mud  process 270 

9.  Diagram  of  crushing  and  transverse  tests  made  on  soft-mud  brick  from 

Wisconsin 286 

10.  Diagram  showing  absorption  tests  on  Wisconsin  soft-mud  brick  after 

48  hours'  immersion ; 290 

11.  Diagram  of  crushing  and  transverse  tests  on  Wisconsin  stiff -mud  brick  .  .  291 

12.  Diagram  showing  absorption  tests  on  Wisconsin  stiff-mud  brick  after 

48  hours'  immersion 292 

130.  Diagram  of  crushing  and  transverse  tests  on  Wisconsin  dry-pressed  brick 

136.  Absorption  tests  of  same  series 293 

14.  Different  styles  of  shingle  tile 349 

15.  Old  Spanish  or  Mission  tiles 350 

16.  Section  of  roof  showing  modern  Spanish  tile,  cresting,  hip  rolls  and  finials  351 

17.  Quarry  tile 360 

18.  Finials  for  tile  roof 361 

19.  Graduated  tower  tile.     Spanish  pattern 362 

20.  Sections  of  sewer  blocks 386 


xv 


PART    I. 

BUILDING   STONES. 


BUILDING  STONES   AND 
CLAY-PRODUCTS. 


CHAPTER   I. 

ROCK  MINERALS  AND  ROCKS. 

INTRODUCTION. 

UNDER  the  term  Building  Stones  are  included  all  those  rocks 
which  are  employed  for  ordinary  masonry  construction,  such 
as  walls  and  foundations,  for  ornamentation,  roofing  and  flagging. 

Many  different  stones  are  used  for  structural  work,  and,  owing 
to  the  abundance  of  these  in  nearly  all  parts  of  the  United 
States,  as  well  as  the  growing  demand  for  this  class  of  building 
material,  the  industry  has  assumed  proportions  of  considerable 
size. 

The  total  quantity  of  stone  quarried  annually  in  the  United 
States  is  large,  but  all  of  it  is  not  employed  for  structural  work. 
An  attempt  has  been  made,  however,  to  separate  the  value  of 
that  so  used  from  that  consumed  in  other  industries  with  the 
following  results,  the  figures  being  taken  from  the  1910  report 
on  Mineral  Resources,  issued  by  the  United  States  Geological 
Survey. 

APPROXIMATE  VALUE  OF  BUILDING  STONE  PRODUCED  IN  1910. 

Granites $10,325,874 

Trap  rock 87,832 

Sandstone 2,272,024 

Bluestone 518,660 

Limestone 5,272,024 

Marble 8,980,240 

$27,456,654 

Practically  every  state  produces  some  building  stone,  and  many 
quarries  are  operated  only  for  local  use,  partly  because  the  weight 
of  stone  prohibits  long  hauls  unless  the  material  is  of  high  grade. 

3 


"4V  BUILDING   STONES   AND   CLAY-PRODUCTS 

*"cBy*firf  the  larger  part  of  the  building  stone  quarried  is  for 
ordinary  dimensional  work  and  may  be  sold  in  the  rough  to 
be  dressed  later.  This  applies  chiefly  to  granite,  sandstone, 
limestone  and  trap. 

For  ornamental  work,  and  this  calls  for  a  considerable  quantity 
of  stone,  the  material  has  to  meet  varying  requirements.  In  the 
first  place  it  should  lend  itself  to  carving,  and  that  some  stones 
serve  this  purpose  well  is  shown  by  the  many  intricate  and  beauti- 
ful designs  on  buildings  and  monuments.  For  monumental 
work,  also,  and  decorative  work,  a  highly  polished  surface  is  often 
wanted,  and  the  granites,  marbles  and  serpentines  are  usually 
found  well  adapted  to  this  need. 

Inscriptional  work  necessitates  the  selection  of  a  stone 
that  will  give  good  contrast  between  the  cut  and  polished 
surface,  a  character  found  in  many  of  the  darker  granites  and 
marbles. 

In  considering  the  selection  of  a  building  stone,  the  architect 
is  usually  guided  either  by  cost  or  decorative  value,  the  dura- 
bility or  weather-resisting  qualities  of  the  material  being  some- 
times overlooked.  The  latter  is  a  serious  neglect  if  the  stone  is 
to  be  employed  for  exterior  work  in  a  severe  climate. 

Most  of  the  building  stone  employed  for  constructional  work 
in  this  country  is  from  domestic  sources,  and  not  a  little  decora- 
tive stone  is  also  obtained  here ;  but  large  quantities  of  varie- 
gated marble  for  ornamental  purposes,  and  even  some  other 
kinds  of  stone,  are  imported  from  foreign  countries. 

This  can  hardly  be  due  entirely  to  the  non-existence  of  such 
materials  in  the  United  States,  but  rather  perhaps  to  the  reluc- 
tance of  American  quarrymen  to  incur  the  risk  and  expense  of 
placing  a  new  stone  on  the  market  in  competition  with  the 
foreign  ones  already  so  widely  used.  The  factors  which  may  be 
said  to  influence  the  selection  of  a  building  stone,  arranged  in 
the  order  of  importance  apparently  assigned  to  them  by  many, 
are  cost,  color,  fashion  and  durability. 

The  cost  will  naturally  be  a  dominant  factor  in  the  selection 
of  a  stone,  and  depends  on  its  location,  ease  of  quarrying,  dress- 
ing and  beauty. 


ROCK  MINERALS  AND  ROCKS  5 

Color  often  exercises  a  determining  influence,  and  this,  com- 
bined with  other  considerations,  sometimes  starts  a  fashion 
which  leads  to  the  widespread  use  of  certain  stones.  An  excel- 
lent illustration  of  this  was  the  selection,  for  many  years,  of  the 
Connecticut  brownstone  in  many  eastern  cities.  More  recently 
Indiana  limestone  and  Ohio  sandstone  have  met  the  popular 
fancy,  and  these  two  are  now  used  in  vast  quantities. 

Durability  is  often  apparently  given  little  consideration  where 
a  stone  of  high  decorative  character  is  sought,  although  it  should 
in  every  instance  be  a  factor  of  primary  importance. 

A  study  of  the  properties  of  building  stones  can  hardly  be 
taken  up  without  some  knowledge  of  their  mineral  constituents, 
or  at  least  the  common  minerals  which  occur  in  them,  because 
these  are  used  for  purposes  of  identification  and  individually 
influence  the  different  properties  of  the  stone  to  a  marked  degree. 
The  number  of  important  or  essential  minerals  in  building  stones 
are  comparatively  few,  but  in  addition  to  these  there  are  many 
of  subordinate  rank,  often  in  such  small  grains  as  to  be  scarcely 
visible  to  the  naked  eye.  Their  presence  may  be  of  scientific 
interest,  but  the  majority  of  them,  except  when  present  in  large 
amount  (and  this  is  rare),  exert  but  little  influence  on  the 
character  of  the  rock. 

ROCK-FORMING  MINERALS.1 

A  mineral  may  be  defined  as  a  natural  inorganic  substance 
of  definite  chemical  composition  occurring  in  nature. 

There  are  a  great  many  known  mineral  species,  but  only  a 
very  small  number  are  important  constituents  of  building  stones. 
Not  a  few  others  are  present  in  very  small  amounts,  —  scattered 
grains,  —  sometimes  of  microscopic  size.  These  in  many  cases 
have  little  or  no  effect  on  the  quality  of  the  stone. 

Physical  Properties.  In  the  determination  of  minerals,  cer- 
tain physical  characters,  such  as  the  cleavage,  hardness,  lustre 
and  crystal  form,  are  commonly  made  use  of,  and  in  the  study 

1  Those  desiring  to  read  up  the  subject  of  rock-forming  minerals  in  more  de- 
tail are  referred  to  Dana,  "  Minerals  and  How  to  Study  Them  "  (Wiley  &  Sons); 
also  Hatch,  "Mineralogy"  (Whittaker  and  Co.). 


6  BUILDING  STONES   AND    CLAY-PRODUCTS 

of  rocks,  by  means  of  thin  sections  examined  under  the  micro- 
scope, the  optical  properties  of  the  minerals  are  of  great  diag- 
nostic importance. 

The  more  important  physical  properties  may  now  be  denned. 

Hardness.  The  different  mineral  species  usually  show  a 
definite  degree  of  hardness,  and  this  property  can  be  expressed 
numerically,  with  reference  to  a  graded  scale  of  10  minerals, 
ranging  from  those  which  are  very  soft  to  the  hardest  ones 
known.  This  scale  is  as  follows: 

1.  Talc.  6.   Orthoclase. 

2.  Gypsum.  7.   Quartz. 

3.  Calcite.  8.   Topaz. 

4.  Fluorite.  9.    Sapphire. 

5.  Apatite.  10.   Diamond. 

Any  member  of  the  series  will  scratch  any  of  the  others  below 
it.  Talc  is  readily  scratched  by  the  finger  nail,  and  gypsum  with 
difficulty.  A  good  steel  blade  will  barely  scratch  orthoclase,  and 
quartz  is  sufficiently  hard  to  scratch  glass. 

The  hardness  of  any  other  mineral  can  be  determined  by 
testing  it  with  those  of  the  hardness  scale.  Thus  if  a  mineral 
is  scratched  by  quartz  but  not  by  orthoclase,  its  hardness  is  6. 

Cleavage.  Many  minerals  possess  the  property  of  splitting 
more  or  less  readily  in  certain  directions.  This  is  termed  the 
cleavage.  Some  minerals  exhibit  but  one  system  of  cleavage 
planes,  others  two  or  three.  These  cleavage  systems  intersect 
each  other  at  definite  angles.  In  orthoclase  feldspar,  for  exam- 
ple, the  cleavage  planes  cause  the  mineral  to  break  off  with 
square  corners.  Cleavage  planes  may  be  parallel  to  crystal 
faces. 

Lustre.  Minerals  often  show  a  more  or  less  characteristic 
lustre  on  either  the  crystal  faces,  cleavage  planes,  or  fracture 
surfaces.  These  lustres  may  be  designated  as  vitreous,  pearly, 
resinous,  dull,  earthy,  metallic,  etc.  Quartz  shows  a  vitreous 
lustre,  and  gypsum  a  pearly  one. 

Form.  If  minerals  have  room  to  grow,  they  usually  form  crys- 
tals of  definite  outline,  bounded  by  plane  faces,  but  in  most 


ROCK   MINERALS   AND    ROCKS  7 

rocks  formed  by  the  crystallization  of  minerals  these  are  so 
crowded  that  they  have  no  space  to  grow  freely  and  complete 
their  form.  The  grains  are  therefore  termed  crystalline. 

Having  described  briefly  the  common  physical  properties,  the 
more  important  minerals  found  in  building  stones  may  next 
be  taken  up. 

Quartz.  This  mineral,  which  is  composed  of  silica,  is  a  very 
abundant  one  in  many  building  stones.  It  is  insoluble  in  all 
acids,  except  hydrofluoric,  has  a  hardness  of  seven,  no  cleavage, 
a  vitreous  lustre,  and  a  specific  gravity  of  2.6. 

If  pure  it  is  transparent  and  colorless,  but  more  often  it  is 
milky  white,  and  small  amounts  of  impurities  may  give  it  differ- 
ent colors.  It  is  very  resistant  to  the  weather. 

Flint  and  chert  are  amorphous  or  non-crystalline  forms  of 
silica,  often  of  dark  color,  and  form  concretionary  masses  in 
certain  rocks,  especially  limestones  (Plate  XXXI,  Fig.  i). 

Quartz  is  a  common  and  important  constituent  of  some 
igneous  and  metamorphic  rocks  and  sandstones. 

Feldspars.  The  feldspars  are  essentially  silicates  of  alumina, 
with  potash,  soda  or  lime.  Orthoclase  and  plagioclase  are 
species  of  feldspar. 

Orthoclase.  This  is  a  silicate  of  alumina  and  potash,  but  some 
of  the  latter  may  be  replaced  by  soda.  Its  hardness  is  6  and  the 
specific  gravity  2.54-2.56.  It  shows  two  sets  of  cleavage  planes 
which  intersect  at  right  angles.  Its  lustre,  on  the  cleavage 
planes,  is  somewhat  glassy,  and  the  color  is  commonly  pink, 
sometimes  very  deep,  less  often  whitish.  Weathering  destroys 
the  lustre  and,  if  carried  to  completion,  converts  the  mineral 
into  a  white  clayey  mass. 

It  is  a  common  constituent  of  granites  and  many  gneisses, 
and  may  be  present  in  sandstones. 

Orthoclase  is  less  durable  than  quartz,  with  which  it  is  fre- 
quently associated,  but  is  not  to  be  regarded  as  unsafe  on  this 
account. 

Plagioclase  Feldspars.  Under  this  head  are  grouped  several 
feldspar  species,  which  are  silicates  of  alumina  with  soda  or 
lime.  They  agree  with  orthoclase  in  hardness,  but  range  from 


8  BUILDING  STONES  AND   CLAY-PRODUCTS 

2.62  to  2.75  in  specific  gravity.  The  plagioclases  are  usually 
white  in  color,  and  on  certain  cleavage  planes  show  fine  parallel 
lines.  This,  with  their  color,  usually  serves  to  distinguish 
them  from  orthoclase.  They  are  less  durable  than  the  latter, 
but  not  sufficiently  short-lived  to  cause  the  rejection  of  a  stone 
containing  them. 

Plagioclase  is  a  common  constituent  of  some  igneous  rocks, 
such  as  diorite,  diabase  and  gabbro,  in  which  quartz  is  rare  or 
absent. 

Micas.  Building  stones,  especially  granites  and  gneisses, 
often  contain  two  kinds  of  mica  as  prominent  constituents. 
These  are  the  white  mica,  or  muscovite,  and  the  black  mica,  or 
biotite.  They  are  minerals  of  complex,  as  well  as  somewhat 
variable,  chemical  composition,  but  the  former  is  essentially  a 
silicate  of  alumina  and  potash,  while  the  latter  is  a  silicate  of 
iron,  alumina,  magnesia  and  potash. 

They  occur  in  the  rocks  in  the  form  of  small  shining  scales, 
sometimes  of  six-sided  character,  with  a  very  perfect  cleavage, 
which  causes  them  to  split  readily  into  thin  elastic  leaves. 

Muscovite  is  silvery  white  in  color,  has  a  strong  lustre,  and 
is  transparent  in  thin  leaves.  Its  hardness  is  2. -2. 5. 

Sericite  is  a  very  fine  grained,  silvery  or  light  green  type  of 
muscovite,  formed  by  the  alteration  of  feldspar. 

Biotite  is  black  or  dark  green  in  color,  when  in  thick  plates 
or  masses,  but  differs  but  little  from  muscovite  in  its  lustre,  al- 
though its  hardness  is  slightly  greater,  i.e.,  2.5-3. 

Phlogopite,  a  nearly  colorless  mica  resembling  muscovite, 
is  not  uncommon  in  some  crystalline  limestones  and  serpentines. 

Of  the  several  kinds  of  mica,  the  muscovite  is  little  affected 
by  the  weather,  but  the  biotite,  on  account  of  its  high  iron  con- 
tent, is  more  liable  to  decompose  on  exposure  to  the  weather. 

The  kind,  quantity  and  distribution  of  mica  in  a  building 
stone  exerts  an  important  influence  on  its  durability  and  work- 
ability. 

If  present  in  abundance,  and  the  scales  are  arranged  in  parallel 
layers,  the  rock  may  split  readily  along  these  planes.  Such 
stones,  especially  sandstones,  should  be  set  on  bed. 


ROCK  MINERALS  AND   ROCKS  9 

Mica,  if  abundant,  is  also  an  undesirable  ingredient  of  marble 
used  for  exterior  work,  as  it  weathers  out  easily  and  leaves  a 
pitted  surface. 

It  is  difficult  to  polish  and  therefore  affects  the  continuity  of 
the  polished  surface  of  a  rock  containing  it. 

Some  building  stones,  such  as  granite,  are  rarely  free  from  it, 
but  in  these  it  is  not  regarded  as  an  injurious  constituent  unless 
present  in  large  quantity. 

The  micas  may,  on  account  of  their  color,  exert  a  strong  effect 
in  this  direction. 

Amphibole.  This  mineral,  which  is  a  complex  silicate,  has  a 
number  of  varieties,  of  which  hornblende  is  the  most  important 
in  building  stones.  Tremolite  is  another. 

Hornblende  is  a  silicate  of  iron,  lime,  magnesia  and  alumina. 
It  is  dark  green,  brown  or  black  in  color,  and  occurs  in  compact, 
sometimes  bladed,  crystals  of  fair  lustre.  It  resembles  biotite 
but  does  not  split  into  thin  leaves  as  the  latter  does.  Its  hard- 
ness is  5-6.  Unlike  biotite  mica,  hornblende  takes  a  polish 
and  shows  a  better  resistance  to  the  weather  than  that  mineral. 

Hornblende  is  an  important  constituent  of  many  igneous 
rocks  and  of  some  metamorphic  gneisses  and  schists. 

Tremolite  (Plate  XXXI,  Fig.  2)  is  a  pale-green  variety  of 
amphibole  found  in  some  crystalline  limestones.  It  occurs  in 
blade-like  or  silky-looking  masses  and  is  a  detrimental  mineral, 
since  it  tends  to  decompose  to  a  greenish-yellow  clay. 

Pyroxene.  This  is  a  common  mineral  in  some  igneous  rocks, 
especially  the  darker-colored  or  basic  ones.  Its  composition 
and  colors  are  similar  to  those  of  amphibole,  from  which  it  often 
cannot  be  distinguished  with  the  naked  eye  when  found  in  build- 
ing stones.  The  dark-colored  variety,  augite,  is  an  essential 
constituent  of  some  igneous  rocks,  such  as  diabase  and  basalt, 
but  may  occur  in  other  more  acid  ones. 

Other  varieties  of  pyroxene  may  be  present  in  either  igneous  or 
metamorphic  rocks  but  are  not  always  visible  to  the  naked  eye. 

Augite  takes  a  good  polish  and  shows  fair  durability. 

Merrill  states  that  the  "  pyroxene  of  the  Quincy,  Mass.,  granite 
proves  to  be  an  exceptionally  brittle  variety,  and  the  continued 


10  BUILDING  STONES  AND   CLAY-PRODUCTS 

breaking  away  of  little  pieces  during  the  process  of  dressing  the 
stone  makes  the  production  of  a  perfectly  smooth  surface  a 
matter  of  great  difficulty. " 

Calcite.  This  mineral  consists  of  carbonate  of  lime  (CaCO3). 
It  is  white,  when  pure,  and  has  a  hardness  of  3 ;  hence  it  is  soft 
enough  to  be  scratched  with  a  knife.  It  effervesces  readily 
when  a  drop  of  dilute  acid  is  put  on  it. 

Calcite  is  an  important,  and  sometimes  the  only,  constituent 
of  many  limestones,  marbles  and  onyxes.  Calcareous  shales 
contain  a  variable  quantity  of  it. 

It  may  also, occur  as  a  secondary  constituent  of  many  igneous 
rocks,  having  been  formed  by  the  decomposition  of  other  minerals, 
but  in  such  cases  it  is  usually  present  in  but  small  amounts. 

Sandstones  may  have  some  calcite  as  a  cementing  material. 
When  exposed  to  the  weather,  calcite  is  dissolved  by  waters, 
especially  those  containing  a  little  acid.  The  action  is  usually 
slow,  but  its  effect  is  sometimes  seen  in  limestone  quarries  where 
the  rock  has  been  dissolved  out  to  a  variable  depth  along  the 
joint  planes. 

Aragonite,  which  has  the  same  chemical  composition  as  cal- 
cite but  differs  from  it  in  crystalline  form  and  specific  gravity, 
occurs  in  some  onyx  marbles. 

Dolomite.  This  mineral,  which  is  a  double  carbonate  of  lime 
and  magnesia,  (CaMg)COs,  is  much  like  calcite,  but  differs  from 
it  in  being  slightly  harder  and  in  effervescing  only  with  hot 
dilute  acid.  It  is  a  common  constituent  of  many  limestones 
and  marbles.  Dolomite  is  less  soluble  in  surface  or  rain  waters 
than  calcite  but  disintegrates  more  readily  than  the  latter 
does. 

Gypsum.  This  is  a  hydrous  sulphate  of  lime  (CaSO4  +  2  H2O) 
and  is  not  present  in  many  building  stones;  indeed,  it  occurs 
only  in  stratified  rocks.  The  mineral  is  soft  enough  to  be 
scratched  with  the  thumb  nail,  and  its  softness,  together  with 
the  fact  that  it  is  not  acted  on  by  acids,  serve  to  distinguish  it 
from  calcite. 

Alabaster  is  a  fine-grained,  white  variety,  showing  a  trans- 
lucency  in  thin  plates. 


ROCK  MINERALS  AND  ROCKS  II 

Gypsum,  though  occurring  in  beds,  is  of  little  value  for  struc- 
tural work. 

Serpentine.  Serpentine  is  a  green  or  yellowish  material,  of 
soapy  feel,  without  cleavage  and  soft  enough  to  be  easily  cut 
with  a  knife.  Chemically  it  is  a  hydrous  silicate  of  magnesia 
(Mg3Si207  +  2  H20). 

It  is  a  common  and  important  constituent  of  the  serpentine 
or  verd  antique  marbles  used  for  decorative  work,  and  in  these 
occurs  mixed  with  calcite  or  dolomite. 

Its  low  resistance  to  the  weather  is  mentioned  later. 
Talc  or  steatite  is  a  hydrous  magnesium  silicate  [H2Mg3 
(SiOs)^.  It  is  very  soft,  softer  even  than  gypsum,  and  occurs 
commonly  in  the  form  of  small  greenish  scales.  It  resembles 
mica,  but  the  soapy  feel,  softness,  and  absence  of  elasticity  in 
the  scales  serve  to  distinguish  it  from  that  mineral. 

It  is  commonly  an  alteration  product  of  minerals  such  as  horn- 
blende, augite,  mica,  etc.  When  it  occurs  in  massive,  somewhat 
impure  form  it  is  called  soapstone,  a  material  extensively  used  for 
sinks,  washtubs,  etc. 

Olivine.  This  mineral,  known  also  as  chrysolite  and  peridot, 
is  a  silicate  of  iron  and  magnesia  [(MgFe^SiOJ. 

It  has  a  hardness  of  6-7,  glassy  lustre,  and  is  often  of  bottle- 
green  color,  so  that  the  rounded  grains,  if  fresh,  are  easily  recog- 
nizable in  certain  rocks,  of  which  they  sometimes  form  a  charac- 
teristic ingredient.  Olivine  changes  easily  to  serpentine. 

Garnet.  A  silicate  of  alumina,  lime,  iron  or  magnesia,  whose 
hardness  is  6-7,  color  often  red,  and  occurring  in  rounded  grains. 
It  is  not  uncommon  in  some  rocks,  such  as  mica  schist,  gneiss, 
granite  or  crystalline  limestone. 

The  color  and  form  cause  garnets  to  be  readily  recognized. 
Garnets  are  undesirable  constituents  of  building  stones,  as, 
owing  to  their  brittleness  and  hardness,  they  break  away  from 
the  stone  in  the  process  of  dressing  and  interfere  with  the  pro- 
duction of  a  smooth  surface. 

Chlorite  is  a  micaceous  mineral  or  group  of  minerals  which 
occur  as  secondary  products  in  some  igneous  and  metamorphic 
rocks  and  may  impart  a  green  color  to  them. 


12  BUILDING  STONES  AND   CLAY-PRODUCTS 

Pyrite  or  Iron  Pyrite,  an  iron  disulphide  (FeS2),  is  common  in 
all  kinds  of  rocks.  Its  yellow  color  and  metallic  lustre  make  it 
easily  recognizable.  When  in  grains  large  enough  to  be  seen, 
it  is  found  to  form  small  cubes  or  irregular  masses. 

It  is  an  undesirable  constituent  of  building  stones,  especially 
ornamental  ones,  since  it  weathers  somewhat  easily  to  limonite, 
producing  a  rusty  stain  or  causing  disintegration  of  the  rock. 

Another  form  of  iron  sulphide,  marcasite,  decomposes  even 
more  readily. 

Magnetite,  or  magnetic  iron  ore  (Fe3O4),  occurs  as  minute 
grains  in  many  dark-colored  igneous  rocks  (diabase,  basalt, 
etc.),  but  is  usually  identifiable  only  on  microscopic  examination. 

On  exposure  to  the  atmosphere  it  may  change  to  the  sesqui- 
oxide,  causing  a  rusty  stain  on  the  rock. 

Limonite,  a  hydrous  oxide  of  iron  (2  Fe203,  3  H20),  is  a  com- 
mon cement  of  many  rocks,  and  is  also  formed  by  the  decom- 
position of  pyrite,  and  of  iron-bearing  silicates  such  as  biotite, 
hornblende  or  garnet.  It  is  of  a  yellowish-brown  or  brown  color 
and  non-crystalline  character. 

ROCKS.1 

A  rock  may  be  defined  as  a  natural  aggregation  of  minerals 
forming  a  portion  of  the  earth's  crust. 

According  to  their  mode  of  origin,  rocks  can  be  divided  into 
three  great  groups,  the  igneous,  stratified  and  metamorphic. 

The  origin  and  essential  characters  of  these  may  be  briefly 

referred  to. 

IGNEOUS  ROCKS. 

These  have  been  formed  by  the  cooling  of  a  molten  mass, 
or  magma,  which  has  come  up  from  some  variable  and  unknown 
depth  in  the  earth's  interior.  As  it  cooled,  the  different  minerals 
crystallized  out  to  form  a  more  or  less  tightly  interlocking  mass. 
The  rock  in  some  cases  has  solidified  before  reaching  the  surface, 
while  in  others  it  has  flowed  out  on  the  surface  as  a  lava  stream. 

1  For  more  details  than  can  be  given  here  see  Scott,  "Introduction  to  Geol- 
ogy" (Macmillan  Co.);  Kemp,  "Handbook  of  Rocks"  (Van  Nostrand);  Pirsson, 
'Rocks  and  Rock  Minerals"  (Wiley  and  Sons). 


PLATE  I.  —  A  small  fine-grained  dike  of  dark  diabase  cutting  a  lighter-colored 
syenite.    These  dikes  may  be  very  narrow,  or  many  feet  in  width. 


PLATE  II.  —  A  volcanic  rock,  trachyte,  showing  porphyritic  texture. 


ROCK  MINERALS  AND  ROCKS  17 

Those  which  cooled  below  ground  are  known  as  plutonic 
rocks  and  show  varying  forms,  while  those  which  have  cooled 
on  the  surface  are  termed  volcanic  rocks. 

Some  masses  of  igneous  rock  are  long  and  narrow  (dikes), 
while  others  are  irregular,  or  rudely  dome-shaped  in  character 
(bathyliths  and  bosses). 

With  few  exceptions,  they  agree  in  being  of  a  massive  struc- 
ture, more  or  less  crystalline  in  texture,  and  free  from  strati- 
fication planes.  They  differ  in  their  texture,  however,  some 
being  fine  grained,  others  coarse  grained. 

Some  are  even  textured  (Plate  III,  Fig.  i),  while  others  show 
a  groundmass  of  small  crystalline  grains,  embedded  in  which 
are  larger  ones,  often  of  distinct  crystal  outline;  this  latter  type 
of  texture  is  termed  porphyritic  (Plate  II). 

In  some  cases  lavas  approaching  the  surface  in  the  vent  of  a 
volcano  are  blown  out  with  such  force  as  to  be  disrupted  into  a 
mass  of  large  and  small  fragments,  which  settle  down  on  the 
surface.  The  coarser  material  is  often  called  volcanic  breccia, 
while  the  finer-grained  deposit  is  termed  tuff  or  ash.  These 
ash  deposits  become  subsequently  cemented  somewhat  by  the 
action  of  rain  water. 

In  some  countries,  as  Mexico,  volcanic  breccias  and  tuffs  are 
extensively  used  for  building  purposes. 

Igneous  rocks  are  differentiated  or  classified  on  the  basis  of 
their  mineralogical  composition  and  texture. 

The  volcanic  rocks  may  be  glassy,  cellular  or  porphyritic. 
The  plutonic  ones  are  usually  massive  and  holocrystalline,  por- 
phyritic textures  being  rare,  except  in  the  dike  rocks. 

A  rock  might,  therefore,  preserve  a  uniform  mineral  composi- 
tion, but  vary  in  its  texture,  depending  upon  the  conditions  under 
which  it  cooled. 

On  the  other  hand,  several  plutonic  rocks  might  agree  in 
their  texture,  but  differ  in  their  mineralogical  make-up. 

These  differences,  either  mineralogical  or  textural,  lead  to  the 
development  of  different  species. 

The  following  table,  taken  from  Pirsson,  expresses  simply  the 
mineralogical  and  textural  relationships  of  the  more  common  types : 


i8 


BUILDING  STONES  AND   CLAY-PRODUCTS 


A.   Grained,  Constituent  Grains  Recognizable,  Mostly  Intrusive. 


Non-porphyritic. 

a.   Feldspathic  rocks,  usually  light 
in  color. 

b.   Ferromagnesian  rocks,  generally 
dark  in  color  to  black. 

With  quartz. 

Without  quartz. 

With  subordinate 
feldspar. 

Without  feldspar. 

Granite. 

Syenite, 
a.   Syenite. 
Anorthosite. 

Diorite. 
Gabbro. 
Dolerite. 
Diabase. 

Peridotite. 
Pyroxenite. 

Porphyritic. 

Granite  porphyry. 

Syenite 
porphyry. 

Diorite 
porphyry. 

B.    Dense,  Constituents  Nearly  or  Wholly  Unrecognizable.     Intrusive  and  Extrusive. 


Non-porphyritic. 

a.  Light  colored, 
usually  felds- 
pathic. 

b.   Dark  colored 

to  black,  usually  ferromagnesian. 

Felsite. 

Basalt. 

Porphyritic. 

Felsite  porphyry. 

Basalt  porphyry. 

C.   Rocks  Composed  Wholly  or  in  Part  of  Glass,  Extrusive. 


Non-porphyritic.         Obsidian,  pitchstone,  pumice. 


Porphyritic. 


Vitrophyre. 


D.   Fragmental  Igneous  Material.     Extrusive. 


Tuffs,  Breccias  (Volcanic  ashes,  etc.) 


The  above  classification  includes  nearly  all  the  more  impor- 
tant rocks  which  are  used  for  building  purposes.  There  are 
many  others  but  they  are  rarely  used  for  structural  or  monu- 
mental work. 

Those  mentioned  in  the  above  table  may  now  be  briefly 
denned. 

Granites  (Plates  III,  IV).  These  consist  essentially  of  quartz, 
orthoclase  feldspar  (sometimes  microcline).  Some  species  of 
mica,  amphibole  or  pyroxene  is  usually  present,  and  a  number 
of  others  may  occur  as  accessories,  but  they  are  usually  of  micro- 
scopic size.  The  texture  is  holocrystalline  but  varies  from 
coarse  to  fine.  Granites  are  sometimes  classified  according  to 
some  prominent  accessory  mineral,  as  muscovite,  etc. 

Pegmatite  (Plate  V)  is  a  granite,  usually  of  very  coarse  grain, 
and  occurring  commonly  in  the  form  of  dikes.  It  is  of  no  value 


PLATE  III,  Fig.  i.  —  Moderately  fine-grained  granite,  Hallowell,  Me. 


PLATE  III,  Fig.  2.  —  Very  coarse-grained  granite,  St.  Cloud,  Minn. 


PLATE  IV.  —  Coarse-grained,  somewhat  porphyritic  granite 
from  Crotch  Island,  Me. 


21 


ROCK  MINERALS  AND  ROCKS  23 

as  a  building  stone,  but  the  occurrence  of  dikes  of  it  in  some 
quarries  causes  a  serious  waste. 

Syenite.  This  is  an  even  granular  rock,  composed  chiefly  of 
orthoclase  feldspar  and  differing  from  granite  only  in  the  absence 
of  quartz.  Mica,  hornblende  or  pyroxene  are  usually  present. 
Syenites  are  sometimes  porphyritic  and  grade  into  syenite 
porphyry.  They  may  be  white,  pink  or  gray  in  color.  They 
are  not  very  abundant,  and  are  of  little  importance  as  building 
stones. 

Diorite.  This  is  a  granular  intrusive  rock  composed  of  horn- 
blende and  feldspar,  but  often  containing  considerable  biotite 
mica.  The  feldspar  is  a  plagioclase. 

Diorites  are  of  a  dark  gray  or  greenish  color,  sometimes  nearly 
black,  while  the  grain  varies  from  coarse  to  fine. 

Intermediate  forms  between  granite  and  diorite  are  known 
as  granite-diorite.  Monzoniie  is  intermediate  between  syenite 
and  diorite. 

Gabbro.  This  is  also  a  granular  intrusive  rock,  which  consists 
chiefly  of  pyroxene  and  feldspar.  The  latter  may  predominate 
to  such  an  extent  as  to  give  the  stone  a  very  dark  color.  The 
color  is  dark  gray  or  greenish  to  black.  Magnetite  in  small 
black  grains  is  often  present,  and  so,  too,  may  be  olivine. 

It  is  a  common  rock  in  the  United  States,  being  known  in  New 
England,  the  Adirondacks,  in  Maryland,  Minnesota,  the  Rocky 
Mountains  and  California. 

Though  of  value  as  a  building  stone,  its  dark  color  causes 
gabbro  to  be  avoided. 

Peridotite.  A  granular  intrusive  igneous  rock  composed  of 
olivine  and  pyroxene  without  feldspar.  It  is  mostly  very  dark 
in  color. 

Pyroxenite.  This  is  also  a  granular  plutonic  rock,  whose  chief 
mineral  is  pyroxene,  but  which  lacks  olivine. 

Granite  Porphyry.  A  rock  of  porphyritic  texture  and  same 
mineral  composition  as  granite. 

Syenite  Porphyry.  A  porphyritic  rock  with  phenocrysts  of 
feldspar  in  a  groundmass  consisting  chiefly  of  feldspar.  The 
dark  minerals  biotite,  hornblende  or  pyroxene  may  be  present. 


24  BUILDING  STONES  AND   CLAY-PRODUCTS 

Diorite  Porphyry.  Consists  of  phenocrysts  of  hornblende 
and  feldspar  in  a  groundmass  of  the  same  minerals , 

Felsite.  This  is  a  general  term  which  includes  fine-grained 
igneous  rocks  of  stony  texture  and  usually  light  color.  They 
correspond  to  granites  and  syenites  in  mineralogical  composition. 
In  many  cases  the  mineral  grains  are  too  small  to  be  seen  with 
the  naked  eye. 

If  of  porphyritic  character,  and  the  phenocrysts  are  quartz, 
the  rock  may  be  called  rhyolite,  while  if  the  phenocrysts  are 
feldspar  the  name  trachyte  porphyry  is  used. 

Felsites  occur  as  dikes  or  more  often  as  lava  flows  or  sheets. 

They  are  not  uncommon  in  many  parts  of  the  United  States. 

Basalts.  These  correspond  to  the  felsites  in  texture  but  are 
dark  colored.  Mineralogically  they  agree  with  gabbros  or 
diorites.  They  are  gray  black  to  black  in  color,  but  their  appear- 
ance is  less  lustrous  than  that  of  many  felsites. 

Basalt  porphyry  bears  the  same  relation  to  basalt  that  fel- 
site  porphyry  does  to  felsite. 

STRATIFIED  ROCKS. 

This  group  includes  a  series  of  rocks  of  stratified  character 
(Plate  VI);  that  is  to  say,  they  are  made  up  of  layers. 

They  consist  of  material  which  has  been  derived  from  pre- 
existing ones.  To  state  their  origin  briefly  it  may  be  said  that 
when  rocks  are  attacked  by  the  weathering  agents  they  are 
broken  down  by  physical  and  chemical  processes. 

Some  of  the  products  of  decay,  consisting  of  rock  and  mineral 
fragments,  are  washed  down  the  slopes  into  the  streams  and 
carried  by  them  to  the  lakes  or  sea,  on  the  floor  of  which  the 
material  settles  down  as  sediment.  Additional  quantities  may 
be  supplied  by  waves  beating  against  the  rocks  exposed  along 
the  shore.  Other  portions  of  the  rock  masses  referred  to  above 
are  carried  off  in  solution  and  reprecipitated,  perhaps  as  chem- 
ical sediments,  on  the  ocean  floor  or  sometimes  on  the  land,  as 
in  caves,  ponds  or  around  the  mouths  of  springs.1 

1  There  are  other  methods  of  accumulation  but  these  are  the  most  important. 


PLATE  V.  —  Pegmatite,  showing  coarse-grained  texture. 


PLATE  VI,  FIG.  i.  —  View  in  a  limestone  quarry,  showing  the  horizontal 
stratification  planes  and  vertical  joint  planes.     (H.  Ries,  photo.) 


PLATE  VI,  FIG.  2.  —  General  view  of  a  limestone  quarry,  showing  stratified 
character  of  the  rock. 


ROCK  MINERALS  AND  ROCKS  29 

The  accumulation  of  shell  fragments  on  the  ocean  bottom  may 
also  cause  deposits  of  considerable  size  and  extent. 

These  ocean  sediments  may  collect  in  considerable  thickness 
and  become  consolidated  (hardened) ,  in  part  by  pressure  of  many 
feet  of  overlying  beds,  and  in  part  by  the  deposition  of  mineral 
matter  around  the  grains,  which  serves  as  a  cement  to  bind  them 
together. 

Later,  by  the  uplift  of  the  ocean  bottom,  such  rock  masses 
become  elevated  to  form  land. 

Some  stratified  rocks,  however,  as  sand,  gravel  and  clay,  may 
still  remain  soft. 

The  more  important  types  may  be  defined. 

Sandstone.  This  is  a  rock  of  varying  hardness,  whose  grains 
are  chiefly  quartz.  These  grains  are  of  varying  size  and  are 
bound  together  usually  by  silica  or  iron  oxide,  although  lime 
carbonate  and  even  clay  may  also  perform  this  function. 

A  micaceous  sandstone  is  one  containing  mica  scales.  Argil- 
laceous sandstone  is  a  fine-grained  phase  containing  considerable 
clay.  Arkose  is  a  variety  containing  much  feldspar. 

Conglomerate.  This  might  be  defined  as  a  cemented  gravel, 
the  pebbles  of  which  are  more  or  less  rounded,  and  may  be  of 
different  kinds  of  rock.  Conglomerates  vary  in  their  coarseness, 
and  all  gradations  from  a  coarse  quartz  conglomerate  to  a  sand- 
stone may  be  found. 

Shale.  This  is  a  thinly  layered  clay  rock  formed  by  the  con- 
solidation of  clay.  It  is  of  no  value  as  a  building  stone. 

Limestone.  A  rock  consisting,  when  pure,  of  lime  carbonate 
or  calcite  and  showing  varying  degrees  of  purity,  hardness  and 
texture.  Sand  and  clay  are  common  impurities  and  by  an  in- 
crease in  these  the  rock  may  pass  into  sandstone  and  shale. 
Some  varieties  contain  large  quantities  of  shells  and  other  fossils, 
which  may  stand  out  prominently  on  the  weathered  surface. 
Limestones  vary  in  their  color  but  white,  gray  or  black  are 
common  ones.  They  are  usually  fine-grained.  A  drop  of  acid 
causes  violent  effervescence. 

Of  the  varieties  of  limestones,  the  following  are  worth  mention- 
ing in  this  connection: 


30  BUILDING  STONES  AND   CLAY-PRODUCTS 

Chalk,  a  very  soft  limestone  of  earthy  texture  and  usually 
white  in  color. 

Calcareous  tufa,  a  porous  mass  of  lime  carbonate,  deposited 
around  the  mouth  of  springs,  as  in  swamps.  It  often  coats  the 
plants  growing  in  that  locality. 

Travertine  is  formed  in  a  similar  way  but  is  more  massive. 

Onyx,  a  dense,  crystalline  form  of  lime  carbonate,  deposited 
usually  on  the  floor  of  caves  by  percolating  water  carrying  lime. 

Coquina.  A  loosely  cemented  shell  aggregate  like  that  found 
near  St.  Augustine,  Fla. 

Dolomite.  A  rock  composed  of  the  carbonate  of  lime  and 
magnesia.  It  resembles  limestone  in  its  hardness  and  color  but 
often  presents  a  more  sandy  appearance  on  the  weathered  sur- 
face. Effervescence  is  produced  only  with  warm  acid. 

There  is  no  sharp  line  of  division  between  limestone  and  dolo- 
mite, the  two  grading  into  each  other. 

METAMORPHIC  ROCKS. 

Both  igneous  and  stratified  rocks  sometimes  become  deeply 
buried  in  the  earth's  crust,  in  which  position  they  may  be  sub- 
jected to  great  pressure  or  heat,  or  sometimes  both.  Without 
going  into  the  causes  of  this,  it  may  be  simply  stated  that  as  a 
result  of  these  two  forces  acting  on  the  kinds  of  rocks  above 
mentioned,  they  are  often  profoundly  changed  in  their  structure, 
texture,  density  and  even  mineral  composition. 

Metamorphic  rocks  usually  show  a  crystalline  or  grained 
structure;  they  are  dense  and  sometimes  banded.  Certain  ones, 
like  slate,  split  very  regularly  or  with  a  perfect  cleavage.  Some 
rocks  may  be  locally  metamorphosed  by  intrusions  of  igneous 
rock. 

The  following  are  important  types  of  metamorphic  rocks: 

Quartzite.  A  hard  siliceous  rock  derived  from  sandstone  and 
differing  from  the  latter  in  being  harder  and  denser. 

Slate.  A  clay  rock  produced  by  the  metamorphism  of  shale. 
In  the  process  of  change,  the  original  stratification  planes  often 
become  closed  up,  their  position  being  indicated  by  the  so-called 
ribbons  in  the  slate.  A  new  plane  of  splitting,  known  as  the 


ROCK  MINERALS  AND  ROCKS  31 

cleavage,  is  developed,  and  it  is  the  regularity  and  perfection  of  this 
which  makes  the  slate  of  value  for  roofing  purposes.  By  further 
metamorphism  a  slate  may  pass  into  a  schist.  (See  below.) 

The  usual  color  of  slate  is  dark  gray  or  bluish  black,  but  red, 
green  and  purple  ones  are  also  known. 

Phyllite  is  a  slate  in  a  more  advanced  stage  of  metamorphism, 
and  one  in  which  the  mica  scales  are  not  only  more  abundant 
but  also  visible  to  the  naked  eye. 

Marble  is  a  metamorphosed  limestone.  It  is  of  crystalline  or 
grained  texture  and  may  be  either  dolomitic  or  not.  Clayey 
impurities  that  were  present  in  the  original  rock  have  often  been 
transformed  into  silicate  minerals  such  as  mica,  these  new 
minerals  being  frequently  arranged  in  lines  or  belts,  thus  giving 
the  rock  a  banded  structure.  Such  marbles  are  far  less  resistant 
to  the  weather.  Carbonaceous  matter  may  cause  gray  colora- 
tion, sometimes  of  a  streaky  or  banded  character. 

Marbles  are  affected  by  acid  in  the  same  manner  as  their 
unmetamorphosed  equivalents. 

Ophicalcite  is  a  crystalline  limestone  with  grains  or  patches 
of  serpentine. 

Gneiss  (Plate  VII).  This  is  a  banded  or  laminated  metamor- 
phic  rock,  which  corresponds  in  its  mineralogical  composition 
to  granite  or  some  other  plutonic  rock.  Thus  we  might  have  a 
granitic  gneiss,  a  syenitic  gneiss,  etc. 

Schist.  This  is  more  thinly  foliated  than  gneiss,  due  usually 
to  an  excess  of  bladed  or  scaly  mineral  grains  such  as  mica.  The 
different  varieties  are  named  after  some  prominent  component 
mineral  such  as  mica  schist,  hornblende  schist,  quartz  schist,  etc. 

Owing  to  their  thin  and  irregular  foliations,  schists  are  of  little 
value  as  building  stones. 

Schists  may  grade  into  gneisses  on  the  one  hand  and  into 
slates  on  the  other. 

STRUCTURAL  FEATURES  AFFECTING    QUARRYING. 

Two  important  structural  features,  which  affect  quarrying 
operations  and  also  the  market  value  of  the  stone,  are  bedding 
and  joints. 


32  BUILDING   STONES  AND   CLAY-PRODUCTS 

Bedding  (Plate  VI).  This  refers  to  the  separation  of  the  rock 
into  layers  and  is  found  in  all  stratified  rocks.  In  some  areas 
the  rocks  are  in  an  undisturbed  position  and  the  layers  are  hori- 
zontal, while  in  other  portions  of  the  earth's  crust  the  rocks  have 
been  disturbed  by  folding  since  their  formation  and  the  beds 
show  varying  degrees  of  tilt  or  dip. 

The  position  of  the  beds  is  of  importance.  If  they  lie  nearly 
horizontal,  quarrying  is  begun  in  the  upper  layer,  and  only  one 
bed  can  be  quarried  at  a  time.  Moreover,  if  the  good  beds  are 
covered  by  worthless  ones,  these  latter  must  be  first  removed. 

When  a  quarry  is  opened  in  a  hillside,  or  where  the  beds  are 
steeply  upturned,  the  material  in  the  different  layers  can  be 
quarried  at  the  same  time,  and  thus  one  quarry  is  capable  of 
producing  several  kinds  of  stone. 

The  marbles  of  Vermont  are  a  good  example  of  this,  for  there 
can  be  produced,  at  the  same  time  from  the  various  beds,  marbles 
of  pure  white,  cloudy,  light  water  blue  and  dark  bluish  and 
greenish  tints. 

The  bedding  planes  vary  in  their  spacing  in  different  quarries. 
In  some  they  are  widely  separated,  and  consequently  the  rock 
is  very  massive  and  more  expensive  to  quarry,  although  blocks 
of  considerable  thickness  can  be  obtained. 

In  others  the  layers  are  very  thin,  and  few  stones  of  value  are 
obtainable,  but  these  thinly  bedded  rocks,  if  of  sandy  nature,  are 
sometimes  of  value  for  flagging. 

Stratified  rocks  split  somewhat  readily  along  their  bedding 
planes. 

Joints  (Plates  VI  and  XX).  These  are  present  in  all  kinds 
of  rocks  and  represent  fissures  of  varying  length  produced  by 
several  causes,  such  as  shrinkage,  twisting,  crushing,  etc. 

Joints  may  traverse  the  rocks  in  different  directions,  and  those 
which  are  parallel  are  regarded  as  belonging  to  the  same  series. 
There  may  be  one  or  more  series  of  vertical  joints  and  a  set  of 
horizontal  ones,  these  combining  to  break  the  rock  into  blocks 
of  rectangular  or  cubical  character. 

Joints  are  an  advantage  in  that  they  facilitate  the  extraction 
of  the  stone.  They  are  a  disadvantage  if  they  serve  as  a  path- 


PLATE  VII.  —  Biotite  gneiss,  showing  characteristic  banded  structure 
of  this  rock. 


33 


ROCK  MINERALS  AND  ROCKS  35 

way  for  surface  waters  and  weathering  agents  to  enter  the  rock, 
and,  moreover,  they  limit  the  size  of  the  blocks  that  can  be 
extracted  from  the  quarry. 

In  some  cases  an  otherwise  good  stone  may  be  so  cut  up  by 
joints  as  to  be  rendered  worthless  for  any  purpose  except  road 
material. 


CHAPTER  II. 
PROPERTIES   OF  BUILDING   STONE. 

THE  properties  which  have  an  important  bearing  on  the  value 
or  durability  of  a  stone,  or  on  both,  are:  Texture,  hardness, 
color,  density,  absorption,  strength,  resistance  to  frost,  fire, 
abrasion  or  acid  vapors,  and  chemical  composition. 

Many  of  these  exert  a  direct  or  an  indirect  influence  on  the 
durability  or  life  of  a  building  stone,  which  will  be  referred  to  in 
more  detail  later. 

The  properties  enumerated  above  may  next  be  taken  up  in 
some  detail,  as  they  are  nearly  all  of  importance. 

Texture.  By  texture  is  meant  the  grain  of  the  stone.  This 
may  vary  from  coarse  to  fine  or  from  regular  to  irregular.  Most 
limestones  are  fine-grained.  Sandstones,  though  commonly 
fine-grained,  may  show  a  coarse  texture  if  representing  transi- 
tional phases  to  a  conglomerate. 

Marbles  vary  from  the  finest  textured  forms,  like  those  of 
Carrara,  Italy,  and  Alabama,  to  others  so  coarse  as  to  be  unde- 
sirable for  structural  work.  Similar  variations  exist  in  igneous 
rocks.  Many  of  the  latter  may  also  show  a  porphyritic  texture. 

Fine-grained  rocks,  whose  grains  are  closely  fitting,  are  denser 
and  may  also  be  more  durable.  This  is  especially  true  in  granites, 
the  finer- textured  ones  being  of  longer  life  than  the  coarse- 
grained and  the  porphyritic  ones. 

If  the  mineral  particles  are  not  only  large  but  of  unequal 
hardness,  the  softer  ones  disintegrate  more  readily,  thus  leaving 
small  pits  on  the  surface.  Cleavage  cracks  may  also  open  up 
more  easily  in  the  large  than  in  the  small  mineral  grains. 

Hardness.  The  hardness  of  a  rock  and  the  hardness  of  its 
component  minerals  should  not  be  confused.  The  former 
depends  on  several  factors,  such  as  hardness  of  component 
minerals  and  relative  abundance  and  state  of  aggregation.  A 

36 


PROPERTIES    OF    BUILDING    STONE  37 

rock  may  therefore  consist  entirely  of  hard  quartz  grains  and 
yet  be  bound  together  by  so  little  cement  that  it  will  crumble 
under  very  little  pressure.  Another  one  similarly  composed  of 
quartz  grains  may  be  so  well  cemented  by  silica  as  to  show  a 
high  crushing  strength. 

Hawes1  has  shown  that  the  hardness  of  certain  granites,  for 
example,  is  not  due  entirely  to  quartz,  which  is  hard  and  brittle 
and  crushes  under  the  tools,  but  that  it  is  due  to  the  feldspar, 
which  is  of  variable  hardness  and  has  different  cleavages. 

Although  hardness  is  an  important  quality  there  is  no  standard 
method  of  testing  it,  but  the  following  ones  are  sometimes  used. 

Rosiwal,  adopting  Toula's  principle,2  uses  a  piece  of  smooth 
but  unpolished  granite  of  about  2  grams'  weight  and  rubs  it  with 
emery  (of  0.2  mm.  diameter  grain)  upon  a  glass  or  metal  plate  for 
from  6  to  8  minutes  until  the  emery  loses  its  effectiveness.  The 
granite  is  then  weighed  and  its  loss  of  volume  calculated.  Such 
a  test  is  rather  inaccurate. 

A  test  suggested  by  J.  F.  Williams3  consisted  in  noting  the  rate 
of  penetration  of  a  drill  of  a  given  diameter,  or  by  measuring 
the  distance  to  which  such  a  drill  will  penetrate  without  being 
sharpened;  or  it  might  be  possible  to  determine  the  amount  of 
rough-pointed  surface  that  could  be  reduced  to  bush-hammered 
surface  in  an  hour.  To  make  this  last  test  of  value  a  pneumatic 
drill  or  surfacer  should  be  used. 

Color.  Building  stones  may  show  a  variety  of  colors,  including 
white,  brown,  red,  yellow,  gray,  buff,  black,  etc.  These  colors, 
in  many  cases,  are  really  of  a  composite  character,  being  produced 
by  a  blending  of  the  colors  of  the  individual  minerals.  Uni- 
formity of  color  may  be  produced  by  uniformity  of  distribution 
of  the  mineral  grains  or  by  the  rock  being  composed  entirely  of 
one  mineral. 

Among  the  igneous  rocks,  of  which  granite  is  the  most 
commonly  used  for  building  purposes,  a  variety  of  colors  is 
observable.  Reds  and  grays,  both  common  colors  in  granite, 

1  Tenth  Census,  X,  pp.  16-18,  1888. 

2  Verhandl.  K.  k.  geol.  Reichsanstalt,  1896,  p.  488,  and  quoted  by  Dale. 

3  Ann.  Rep.  Ark.  Geol.  Surv.,  I,  1890,  p.  41. 


38  BUILDING  STONES  AND   CLAY-PRODUCTS 

are  dependent  on  the  proportion  of  red  and  white  feldspar.  A 
granite  of  white  feldspar  and  quartz  and  muscovite  mica  is  very 
light  in  color,  especially  if  dressed  with  a  smooth  surface.  Gray 
and  dark  gray  granites  often  owe  their  color  to  an  excess  or 
appreciable  quantity  of  dark  minerals,  such  as  pyroxene,  horn- 
blende and  biotite. 

Some  igneous  rocks  with  labrador  feldspar  have  a  distinctly 
iridescent  color.  The  volcanic  rocks  may  be  either  light  or 
dark  colored,  depending  on  their  mineral  composition,  some 
being  even  black.  Some  diorites,  gabbros  and  diabases  not  un- 
commonly show  a  dull  greenish-gray  color. 

Among  the  sedimentary  rocks  the  different  shades  of  brown, 
red,  buff  and  yellow  are  due  mainly  to  the  occurrence  of  iron 
oxide.  Gray,  blue  and  black  are  commonly  produced  by  car- 
bonaceous matter.  The  white  color  of  sandstones  indicates  the 
presence  of  clean  quartz  grains,  while  the  same  color  in  limestone 
is  due  to  the  predominance  of  calcite  or  dolomite. 

In  the  metamorphic  rocks  the  colors  of  marbles  and  quartzites 
are  due  to  the  same  causes  as  in  limestones  and  sandstones. 
Gneisses  owe  their  color  to  that  of  the  individual  grains. 

Variation  in  Color.  Sedimentary  rocks  occasionally  show  a 
variation  in  color,  not  only  in  the  same  quarry  but  even  within 
short  distances  in  the  same  bed.  This  is  commonly  due  to  irreg- 
ularity of  distribution  of  the  coloring  material,  which  may  be 
disposed  in  regular  bands  or  irregular  spots. 

In  granites  variations  in  color  may  be  due  to  an  increase  or  a 
decrease  in  the  proportion  of  certain  minerals  in  different  parts 
of  the  quarry.  Some  granites  show  dark  and  unsightly  spots, 
caused  by  the  segregation  of  the  darker  minerals. 

Change  of  Color.  This  may  occur  after  the  stone  has  been 
quarried.  In  stones  colored  black  or  gray  by  carbonaceous 
matter  a  slight  fading  is  some  tines  noticeable.  Some  bright 
pink  granites  have  also  been  known  to  fade  on  continued  expos- 
ure to  the  sunlight.  Certain  sandstones,  though  white  or  light 
gray  when  freshly  quarried,  may,  on  exposure,  change  to  buff  or 
brown,  owing  to  changes  within  the  rock.  These  changes  do  not 
necessarily  represent  a  weakening  of  the  stone. 


PROPERTIES    OF    BUILDING    STONE  39 

The  Berea  sandstone  of  Ohio  changes  to  a  buff  color  after  a 
few  years'  exposure,  due  to  the  alteration  of  finely  divided  pyrite 
to  limonite.  In  such  cases  no  harm  results,  but  if  the  iron 
sulphide  (pyrite)  is  in  large  grains  or  lumps  the  limonite  result- 
ing from  it  may  be  carried  in  streaks  over  the  surface  of  the 
stone,  greatly  marring  its  appearance.1 

A  whitish  discoloration  seen  on  the  surface  of  some  stones  is 
an  efflorescence  derived  from  soluble  salts,  contained  within  the 
pores  of  the  rock.  It  is  brought  to  the  surface  by  evaporation 
of  water  contained  in  the  pores  of  the  stone.  In  some  instances 
it  is  traceable  to  the  mortar. 

Dust  from  the  atmosphere  will  speedily  discolor  many  light 
stones,  and  hence  the  use  of  white  marble  for  exterior  work  is 
to  be  avoided  in  many  cities  where  soft  coal  is  extensively  used. 
Architects,  however,  often  show  a  cheerful  disregard  for  such 
precautions.  Such  dirt  will  naturally  adhere  more  strongly  to  a 
rough  than  to  a  smooth  surface. 

Some  green  slates  are  liable  to  change  color  on  exposure  to 
the  atmosphere,  but  this  does  not  necessarily  indicate  loss  of 
strength. 

The  permanence  of  color  of  a  stone  can  oftentimes  be  gauged 
by  a  comparison  of  the  fresh  face  and  weathered  outcrop  at  the 
quarry. 

An  important  property  is  the  contrast  which  a  stone  shows 
between  hammered  and  polished  surfaces.  It  has  to  be  con- 
sidered if  the  stone  is  to  be  used  for  monumental  or  inscriptional 
work,  and  is  most  pronounced  in  those  stones  containing  a  greater 
abundance  of  transparent  feldspar  and  darker  minerals. 

Remarkable  as  it  may  seem,  fashion  is  a  potent  factor  in  the 
selection  of  building  stones.  Some  years  ago  brownstone  was 
used  in  unlimited  quantities,  and  the  monotonous  rows  of 
brownstone  houses  to  be  seen  in  many  eastern  cities  attest  the 
craze  for  this  material.  Incidentally,  it  was  a  costly  one,  for 

1  Streaking  of  a  stone  is  sometimes  caused  by  the  mortar  colors  becoming 
washed  out  of  the  mortar  joints.  A  custom,  thoughtlessly  pursued  by  some  archi- 
tects, is  to  fasten  ironwork  into  the  surface  of  a  light  stone,  with  the  result  that 
the  rust  from  the  iron  invariably  produces  unsightly  streaks 


40  BUILDING  STONES  AND  CLAY-PRODUCTS 

dozens  of  these  buildings  show  the  stone  to  be  disintegrating, 
because  it  was  placed  on  edge  instead  of  on  bed.  Now  the  Berea 
sandstone  and  Bedford  limestones  are  most  used.  One  asks, 
What  next? 

Polish.  The  ability  of  a  stone  to  take  a  polish  depends  on 
its  density  and  the  character  of  the  mineral  constituents.  An 
aggregation  of  the  same  minerals,  or  even  different  minerals  of 
the  same  hardness,  permits  of  the  development  of  a  better  polish 
than  a  mixture  of  minerals  of  varying  hardness.  Quartz,  feld- 
spar and  calcite  take  a  good  polish,  while  hornblende  and  augite 
are  less  favorable.  Micas  are  difficult  to  polish. 

Specific  Gravity  and  Porosity.  The  specific  gravity  of  a  stone 
is  the  weight  of  the  stone  compared  with  that  of  an  equal 
volume  of  water.  In  order  to  determine  it  the  stone  should 
be  first  weighed  dry;  it  should  then  be  saturated  as  nearly  as 
possible  by  boiling  in  distilled  water,  and  weighed  suspended 
in  water.  The  specific  gravity  then  is 

r         D 

G  =  ^s' 

in  which  „  .,. 

G  =  specific  gravity 

D  =  dry  weight, 
5  =  suspended  weight. 

The  average  specific  gravity  of  a  number  of  stones  is  given  by 
Hermann  as  follows: 

Granite 2.65         Basalt 2.9 

§uartz  porphyry 2.6          Lava 2.15 

yenite 2.8          Gneiss 2.65 

Diabase 2.8          Clay  slate 2.7 

Diorite 2.8          Limestone 2.6 

Gabbro 2.95        Dolomite 2.8 

Serpentine 2.6          Gypsum 2.3 

Trachyte  and  andesite. . .  2.7          Sandstone 2.1 

The  weight  of  the  dry  stone  per  cubic  foot  is  obtained  by 
multiplying  its  specific  gravity  by  the  weight  of  a  cubic  foot  of 
water  (62.8  pounds),  but  Buckley  suggests  there  should  be  de- 
ducted from  this  the  weight  of  a  quantity  of  stone  of  the  same 
specific  gravity  equal  in  volume  to  the  percentage  of  the  pore 
space  of  the  stone. 


PLATE  VIII,  Fig.  i.  —  Gray  marble,  Gouverneur,  N.  Y.,  showing  contrast 
between  tooled  and  polished  surface. 


PLATE  VIII,  Fig.  2.  — Gabbro  from  Keeseville,  N.  Y.,  showing  contrast 
between  tooled  and  polished  surface. 

41 


PROPERTIES    OF    BUILDING    STONE 


43 


The  porosity  is  obtained  by  the  formula 


P  =  100 


\W 


— \ 

-S 


in  which 


P  =  per  cent  porosity, 
W  =  saturated  weight, 
D  =  dry  weight, 
5  =  suspended  weight  of  saturated  stone. 

Foerster1  gives  the  following  porosity  determinations  as  made 
by  Hauenschild  and  Lang. 

POROSITY   PERCENTAGE  OF   DIFFERENT   STONES. 


Granite 0.04-0.61 

Syenite i  .38 

Diorite 0.25 

Porphyry o.  29-2 . 75 

Basalt 1.28 

Diabase  breccia o.  18 

Trachyte  tuff 25.07 


Serpentine 0.56 

Sandstones: 

von  Sailing 6.9 

Nebraer 25.5 

Keuper 16.94 

Carrara  marble 0.22 

Tufa 32.2 

Roofing  slates 0.045-0.115 


Buckley's  work  on  Wisconsin  Building  Stones2  gives  the  fol- 
lowing range  of  porosity: 


Granites .... 
Limestones . 
Sandstones . 


0.019-  0.62 

o-55  -13-36 
4.81  -28.28 


Determinations  made  by  the  same  writer  on  Missouri  stones 3 
gave: 


Granites 

Limestone 

Sandstone .  . 


0.255-  1-452 
0.32  -13.38 
7.01  -23.77 


It  is  contended  by  some  that  it  is  of  more  importance  to  deter- 
mine the  porosity  than  the  absorption  since  the  latter  does  not 
show  the  amount  of  water  the  stone  is  capable  of  holding  and 
because  there  is  no  fixed  ratio  between  pore  space  and  absorp- 
tion; moreover  that  the  porosity  together  with  the  size  of  the 

1  Baumaterialienkunde,  I,  p.  13. 

2  Wis.  Geol.  &  Nat.  Hist.  Surv.  Bull.  IV,  p.  400,  1898. 

3  Mo.  Bur.  Geol.  &  Mines,  II,  2nd  Series,  p.  317,  1904, 


44  BUILDING  STONES  AND   CLAY-PRODUCTS 

pores  gives  us  a  better  index  of  the  frost-resisting  qualities. 
Stones  of  high  porosity,  but  small  pores  are  presumably  less 
resistant  to  frost  than  those  of  high  porosity  and  large  pores. 

It  must  be  admitted,  however,  that  in  general  a  stone  of  high 
porosity  shows  high  absorption,  and  that  the  determination  of 
the  latter  gives  us  a  rough  index  of  the  porosity. 

Absorption.  By  this  term  is  meant  the  amount  of  water  which 
a  stone  will  absorb  when  immersed  in  this  liquid,  and  it  should 
not  be  confused  with  porosity  or  the  volume  of  pore  space. 

While  stones  with  low  porosity  can  absorb  little  water,  and 
others  with  high  porosity  may  absorb  considerable  water,  never- 
theless the  absorption  does  not  necessarily  stand  in  any  direct 
relation  to  the  volume  of  pore  space. 

A  high  absorption  is  considered  undesirable,  as  the  freezing 
of  the  water  in  the  pores  of  the  stone  may  cause  it  to  disintegrate, 
but  this  injury  is  often  more  pronounced  in  fine-grained  than  in 
coarse-grained  materials,  for  the  reason  that  in  the  former  the 
-water  can  drain  off  less  readily. 

Dense  rocks,  like  granites,  gneisses,  slates,  marbles,  many 
limestones  and  quartzites,  usually  show  a  very  low  absorption, 
often  under  i  per  cent.  Other  rocks  including  many  sand- 
stones, some  limestones  (especially  soft  ones)  and  volcanic 
rocks  like  tuffs,  may  absorb  from  perhaps  2  up  to  15  per  cent  of 
water. 

Quarry  Water.  Many  rocks,  especially  those  of  the  sedimen- 
tary class,  contain  water  in  their  pores  when  first  quarried.  This 
is  known  as  quarry  water,  and  may  be  present  in  some  stratified 
rocks,  such  as  sandstones,  in  sufficient  quantities  to  interfere 
with  the  quarrying  of  them  during  freezing  weather.  The 
quarry  water  usually  contains  mineral  matter  in  solution,  and 
when  the  liquid  evaporates,  as  the  stone  dries  out,  the  former  is 
left  deposited  between  the  grains,  often  in  sufficient  quantities 
to  perceptibly  harden  the  rock. 

Crushing  Strength.  This  is  a  property  to  which  undue  im- 
portance has  probably  been  attached;  indeed  in  some  cases  it 
may  be  the  only  test  that  is  made  on  a  stone.  It  can  be  safely 
assumed,  as  one  writer  has  said,  that  a  stone  which  "  is  so  weak 


PLATE  IX,  Fig.  i.  —  Photomicrograph  of  a  section  of  granite. 
(Photo  by  A.  B.  Cushman,  from  Ries's  "Economic  Geology.") 


PLATE  IX,  Fig.  2. — Photomicrograph  of  a  section  of  diabase. 
(Photo  by  A.  B.  Cushman,  from  Ries's  "Economic  Geology.") 


45 


PLATE  X.  —  Photomicrograph  of  a  section  of  quartzitic  sandstone. 
(From  Ries's  "Economic  Geology.") 


47 


PROPERTIES    OF    BUILDING    STONE  49 

as  to  be  likely  to  crush  in  the  walls  of  a  building,  or  even  in  a 
window  stool,  cap  or  pillar,  bears  such  visible  marks  of  its  unfit- 
ness  as  to  deceive  no  one  with  more  than  an  extremely  rudi- 
mentary knowledge  on  the  subject."  Few  stones  will,  when 
tested,  show  a  strength  of  under  6000  pounds  per  square  inch, 
and  many,  especially  igneous  ones,  stand  as  high,  20,000  to 
30,000  pounds  per  square  inch. 

To  be  sure,  in  some  large  buildings  a  single  column  or  block 
may  be  called  upon  to  carry  a  heavy  load,  but  even  then  it  prob- 
ably does  not  approach  the  limit  of  strength  of  the  stone. 

Merrill  has  shown  that  the  stone  at  the  base  of  the  Washing- 
ton monument  supports  a  maximum  pressure  of  22.658  tons  per 
square  foot,  or  314.6  pounds  per  square  inch. 

Allowing  a  factor  of  safety  of  twenty  would  only  require 
the  stone  at  the  base  of  the  monument  to  sustain  6292 
pounds  per  square  inch.  Even  at  the  base  of  the  tallest  build- 
ings the  pressure  is  probably  not  more  than  160  pounds  per 
square  inch. 

The  crushing  strength  of  a  stone  is  commonly  obtained  by 
breaking  a  cube  (usually  2-inch)  in  a  special  testing  machine. 
Great  care  should  be  taken  to  see  that  the  cubes  are  prepared 
with  the  sides  smooth  and  exactly  parallel.  In  some  cases, 
instead  of  preparing  the  surface  of  the  cube  carefully,  it  is  only 
made  approximately  smooth  and  bedded  between  the  plates  of 
the  machine  with  pasteboard  or  plaster  of  Paris. 

Unfortunately  there  is  no  standard  size  of  cube  used  for  test- 
ing purposes,  and  this  may  lead  to  variable  results  since  the 
crushing  strength  per  square  inch  does  not  appear  to  vary  directly 
as  the  size  of  the  cube. 

All  cubes  should  be  thoroughly  dried  before  testing. 

The  crushing  strength  of  a  stone  is  dependent  on  the  state  of 
aggregation  of  the  mineral  particles.  In  sedimentary  rocks  it 
depends  on  the  character  and  amount  of  cementing  material 
(Plate  X) ,  while  in  igneous  and  metamorphic  rocks  it  is  depend- 
ent on  the  interlocking  of  the  mineral  grains  (Plate  IX).  This 
interknitting  of  the  minerals  produces  a  higher  crushing  strength 
in  the  two  last-named  classes  of  rocks. 


50  BUILDING   STONES  AND   CLAY-PRODUCTS 

Many  crushing  tests  have  been  published,  but  it  is  not  always 
safe  to  compare  them,  because  the  conditions  of  testing  have 
not  been  uniform. 

Wet  stones  show  a  lower  crushing  strength  than  dry  ones, 
and  exposure  to  repeated  freezings  may  also  lower  the  resistance 
to  crushing. 

The  following  tests  made  by  Buckley  on  Wisconsin  stones 
show  this  to  be  true  in  some  cases: 


CRUSHING  STRENGTH  OF  WISCONSIN  STONES  BEFORE  AND 
AFTER  FREEZING. 


Kind  of  rock. 

Location. 

Crushing 
strength, 
fresh. 

Crushing 
strength, 
frozen. 

Granite                      

Athelstane  

19,988 

10,619 

do 

Berlin 

24,800 

36,000 

do 

do 

45,841 

32,766 

do 

Montello.  ...          .... 

38,244 

3^,O4<; 

Limestone 

Duck  Creek  

24,522 

28,392 

do 

Sturgeon  Bay  

35,970 

20,777 

do                          

Wauwatosa  

18,477 

25,779 

do 

Burlington 

12,827 

7,cc4 

Sandstone 

Presque  Isle 

C,4QC 

c,  Q-2Q 

do 

Dunnville                 .      .  . 

2,722 

7,464 

..do.. 

Port  Wing.  . 

5,  329 

4,399 

Additional  figures  are  given  by  Watson  for  North  Carolina 
sandstone. 

CRUSHING  TESTS  OF  NORTH  CAROLINA  SANDSTONE. 


Percent  absorption. 

Conditions. 

Crushing  strength, 
Ibs.  per  sq.  in. 

42 

fDry  
^  Wet 

$  10,322 
(  11,150 
(     6,962 

1 
[_  Frozen  

{Dry 
7   ' 

1     5>837 

i  5,625 
i  6,875 
(  12,250 

371 

Wet  

i  11,232 

5,637 

Frozen  .  .  . 

)  6,712 

6,287 

1       6,500 

PROPERTIES    OF    BUILDING    STONE 


Tournaire  and  Michelot  found  that  cubes  of  chalk  10  cm.  in 
diameter  showed  a  crushing  strength,  when  wet,  of  18.6  kilo- 
grams; when  air  dried,  of  23.5  kilograms,  and,  when  stove  dried, 
of  86.2  kilograms. 

Stones  usually  weaken  when  subjected  to  continued  or  inter- 
mittent pressure,  and  may  break  considerably  below  their  nor- 
mal ultimate  crushing  strength.  However,  great  difficulty  is 
experienced  in  obtaining  satisfactory  data  on  this  point,  for  the 
reason  that  it  is  difficult  to  tell  within  a  range  of  1000  to  5000 
pounds  the  crushing  strength  of  samples  to  be  tested  (Buckley) . 

The  following  figures  from  tests  by  Buckley  for  Missouri  and 
Wisconsin,  and  by  Marston  for  Iowa,  will  give  some  idea  of  the 
variations  which  exist  in  the  different  groups  of  stones. 


State. 

Kind. 

Range,  Ibs.  per  sq.  in. 

Missouri  

Limestones  

5,714-27,183  on  bed. 

do 

do 

c,774—  2CJ.C77  on  edge 

do 

Sandstone 

4,371—  9,002  on  bed 

do 

do 

3,933—  9,206  on  edge 

do 

Granite 

18,236—19,410  average 

Wisconsin 

Igneous  rocks 

15,009—47,674 

do 

Limestone  . 

6,675—42,787  on  bed. 

do 

do  

7,508—40,453  on  edge. 

do  

Sandstone  

4,340—13,669  on  bed. 

....do  

do  

1,763—12,566  on  edge. 

Iowa  

Limestones  

2,470—16,435 

do 

Sandstones 

3,600—13,000 

Transverse  Strength.  The  transverse  strength  represents  the 
force  required  to  break  a  bar  i  inch  square  resting  on  supports 
i  inch  apart,  the  load  being  applied  in  the  middle.  This  is 
measured  in  terms  of  the  modulus  of  rupture,  which  is  computed 
from  the  formula: 


in  which 


R 


R  =  modulus  of  rupture, 

w  =  weight  required  to  break  stone, 

/   =  distance  between  supports, 

b  =  width  of  stone, 

d  =  thickness  of  stone. 


BUILDING   STONES  AND    CLAY-PRODUCTS 


The  importance  of  this  test  has  not  been  universally  recog- 
nized, and  it  is  therefore  rarely  carried  out.  Many  a  stone  used 
for  a  window  sill  or  cap  has  cracked  under  transverse  strain 
(Fig.  i),  because  its  modulus  of  rupture  in  the  section  used  is 
too  low.  Such  transverse  breaks  are  not  uncommonly  caused 
by  the  settling  of  the  building. 


Fig.  i.  —  Sandstone  broken  by  transverse  strain-caused  by  settling  of  the  building. 

It  is  of  importance  to  note  that  the  transverse  strength  does 
not  appear  to  stand  in  any  direct  relation  to  the  crushing  strength. 

In  a  series  of  samples  tested  from  Wisconsin  and  Missouri 
by  E.  R.  Buckley,  the  following  variation  was  noticed: 

MODULUS  OF  RUPTURE. 


Kind. 

Wisconsin. 

Missouri. 

Granite                                           

2,324.3—3,909  .  7 

Limestone                     

1,164.3—4,659  .  2 

851  .30—3,311  .60 

Sandstone 

362  9—1,324  o 

418   61—1,321    76 

Of  some  interest  also  is  the  following  set  of  tests  taken  from 
the  Report  on  Tests  of  Metals,  etc.,  for  1895,  issued  by  the 
War  Department.  These  represent  the  relative  transverse 
strength  of  stones  in  the  natural  state  and  after  exposure  to 
hot  and  cold  water  baths.  It  will  be  noticed  that  in  every  case 
this  treatment  resulted  in  a  lowering  of  the  transverse  strength. 


PROPERTIES    OF    BUILDING    STONE 


53 


RELATIVE  TRANSVERSE  STRENGTH  OF  STONES  IN  NATURAL 
STATE  AND  AFTER  EXPOSURE  TO  HOT  AND  COLD  WATER 
BATHS. 


GRANITES. 

Description. 

Modulus  of  rupture  per  square  inch. 

Natural 
state, 
total. 

After  exposure  to  hot  and 
cold  water  baths. 

Total. 

Loss. 

Per  cent 
of 

natural 
state. 

From  Braddock  quarries,  near  Little  Rock, 
Ark.              

Pounds. 
1,704 

2,069 
1,423 
1,378 
1,415 
2,335 

Pounds. 
1,244 

2,027 
1,230 

1,053 
1,083 
2,OO2 

Pounds. 
460 

42 
193 
325 
332 
333 

From  Millbridge,  Me.,  "  White  Rock  Moun- 
tain " 

From  Rockville,  Stearns  County,  Minn  
Drakes  granite,  from  Sioux  Falls,  Minn  
From  Branford,  Conn  

From  Troy,  N.  H  

Means.  . 

1.  721 

I.AAO 

281 

8?     7 

MARBLES. 


Rutland  White,  Vt  
Mountain  Dark,  Vt.  ...            

1,202 

2.IOO 

2QI1 
1,408 

911 

7OI 

Sutherland  Falls,  Vt  
From  St.  Joe,  Ark  
FromDeKalb,  St.  Lawrence  County,  N.  Y. 

3,054 
1,615 
1,144 

1,531 
567 
C77 

1,523 
1,048 

611 



From  Kennesaw  quarry,  Tate,  Ga  

1,553 

605 

948 

Means  

i,779 

822 

957 

46.2 

LIMESTONES. 


From  Isle  La  Motte,  Vt  

2,403 

786 

I.7O7 

From  Mount  Vernon,  Ky 

i  ,4.34. 

i  076 

3*8 

From  Beaver,  Carroll  County,  Ark. 

2,860 

2,  24.7 

613 

From  Bowling  Green,  Ky. 

1,^17 

700 

us 

Blue  colored  from  Bedford,  Indiana  

1,867 

0^8 

ooo 

Means  

i,994 

1,173 

821 

58.8 

SANDSTONES. 


From  Cromwell,  Conn. 

2,243 

I    ^OO 

74.3 

From  Worcester  quarry,  East  Long  Meadow, 
Mass.              .             .          .... 

087 

1,180 

2O2 

From  Kibbe  quarry,   East  Long  Meadow, 
Mass  

1,27"? 

6tx 

618 

From  Cabin  Creek,  Johnson  County,  Ark.  .  . 
Quarries  near  Fort  Smith,  Ark 

2,442 

I  761 

890 

I.lSe; 

1,552 
<?76 



From  Olympia,  Wash. 

2,073 

2,207 

224. 

From  Chuckanut,  Wash. 

2,016 

06  1 

I,O<X 

From  Tenino,  Wash.  .  .  . 

667 

323 

344 

Means  

1,683 

I,I2i: 

558 

66  o 

Means  of  all  stones  

65-1 

1  Heated  in  hot-air  oven  to  402°  F 


54  BUILDING  STONES  AND   CLAY-PRODUCTS 

Frost  Resistance.  A  stone  for  building  purposes  should  resist 
the  action  of  frost,  and  its  disintegration  by  this  agency  is  due 
to  the  water  absorbed  by  it  freezing  within  the  pores  of  the 
rock. 

When  water  freezes  it  expands,  and  if  this  water  is  imprisoned 
in  the  pores  of  the  stone  it  may  exert  sufficient  internal  pressure 
to  disrupt  the  same. 

With  other  things  equal,  one  might  expect  a  stone  of  high 
absorption  to  disintegrate  more  easily  than  one  of  low  absorp- 
tion. This,  however,  is  not  always  the  case,  for  there  are  vari- 
able factors  which  affect  the  result. 

Among  these  may  be  mentioned  the  size,  shape  and  distri- 
bution of  the  pores,  and  rigidity  of  the  rock. 

A  rock  with  large  pore  space  may  absorb  a  high  percentage 
of  water  and  yet  not  be  affected,  because  the  water  either  drains 
off  rapidly  or  else  is  forced  outward  through  the  large  pores. 

On  the  other  hand,  a  stone  with  small  pores,  or  crooked  ones, 
retains  longer  the  water  absorbed  by  it,  and  this  on  freezing  often 
exerts  sufficient  internal  pressure  to  split  the  stone. 

The  frost  resistance  of  a  building  stone  is  an  important  prop- 
erty to  determine,  and  laboratory  tests  should  as  far  as  possible 
simulate  the  conditions  to  which  the  stone  is  exposed  when  in 
use. 

The  most  logical  method  consists  in  soaking  the  stone  in 
water  to  fill  the  pores  as  thoroughly  as  possible,  and  then  expos- 
ing it  to  a  temperature  below  freezing.  This  should  be  repeated 
at  least  20  times,  and  any  loss  in  weight  measured  or  any  dis- 
integration noted. 

An  artificial  method  consists  in  soaking  the  stone  in  a  solu- 
tion of  sulphate  of  soda,  and  then  drying  it  out,  the  theory  being 
that  the  growth  of  the  sulphate  of  soda  crystals  in  the  pores  of  the 
rock  exerts  internal  pressure.  The  treatment  is  repeated  a 
number  of  times. 

This  is  much  more  severe  than  the  ordinary  freezing  test, 
and  gives  abnormal  losses  by  disintegration.1 

1  For  further  discussion  of  this  subject  see  Merrill,  "Stones  for  Building  and 
Decoration,"  3rd. ed., p. 463;  Luquer, Trans.  Am. Soc. Civ.  Engr's, Mar.,  1895,  p.  235. 


PROPERTIES   OF   BUILDING    STONE  55 

The  effects  of  alternate  freezing  and  thawing  may  be  shown 
in  several  different  ways,  such  as:  (i)  Formation  of  cracks, 
(2)  detaching  of  grains  from  surface,  and  (3)  loss  of  strength. 

The  second  type  of  loss  might  occur  in  a  laboratory  test 
without  being  accompanied  by  any  serious  disintegration  of  the 
stone,  as  the  surface  of  many  dressed  stones  is  coated  with  partly 
loosened  grains. 

Buckley,  in  a  series  of  tests  made  on  the  Wisconsin  stones, 
subjected  to  thirty-five  alternate  freezings  (outdoors)  and  thaw- 
ings,  found  the  following  losses  in  weight:  Granites  and  rhyo- 
lites,  not  over  0.05  per  cent.  Limestones,  not  over  0.3  per  cent. 
Sandstones,  not  over  0.62  per  cent. 

A  set  of  Missouri  building  stones  tested  by  the  same  author 
gave  the  following  losses:  Limestones,  0.006-0.909  per  cent. 
Sandstones,  o.m  to  0.591. 


Fig.  2.  —  Effect  of  fire  on  granite  columns,  U.  S.  Public  Storehouse,  Baltimore,  Md. 

Fire  Resistance.  It  is  well  known  that  during  the  destruc- 
tion of  a  building  by  fire,  building  stones  often  suffer  serious  dis- 
integration. This  may  be  due  to  unequal  stresses  set  up  within 
the  stone  by  the  exterior  of  a  block  becoming  highly  heated  while 
the  interior  is  still  comparatively  cool,  or  it  may  also  be  caused 
by  the  stone  becoming  first  highly  heated,  and  then  being  sud- 
denly cooled  by  the  application  of  a  stream  of  cold  water. 


56  BUILDING   STONES  AND   CLAY-PRODUCTS 

The  last-mentioned  combination  of  heat  and  cold  seems  in  all 
cases  to  be  productive  of  far  more  destructive  effects  than 
heating  and  subsequent  slow  cooling. 

The  best  form  of  test  to  determine  the  fire  resistance  of  a 
building  stone  consists  of  building  up  a  section  of  masonry  of 
the  stone  to  be  tested. 

This  may  form  the  interior  of  a  chamber  which  can  be  heated 
to  redness,  or  be  built  up  in  an  iron  framework  which  forms  one 
movable  wall  of  a  furnace. 

In  either  case  the  stone  after  being  heated  to  about  1750°  F. 
is  cooled  down  by  a  strong  stream  of  cold  water  from  a  hose. 

Many  stones  after  heating  to  redness  and  slow  cooling  emit 
a  dull  sound  when  struck.  Lime  rocks,  if  heated  above  850°  C., 
calcine  to  quicklime,  but  at  a  lower  temperature  they  are  less  af- 
fected by  heating  and  slow  cooling  than  any  other  rocks.  Granites 
seem  on  the  whole  to  have  a  lower  resistance  than  sand-stones. 
Considered  as  a  class,  however,  building  stones  are  of  low  fire 
resistance,  especially  if  rapidly  cooled.  In  comparative  tests  they 
are  of  ten  found  inferior  to  clay  products  of  non- vitrified  character. 

A  most  interesting  series  of  tests  was  made  some  years  ago  by 
by  W.  E.  McCourt,1  for  the  New  York  and  New  Jersey  Geological 
Surveys,  on  a  series  of  three  inch  cubes. 

The  tests  consisted  in:  i.  Heating  two  cubes  to  550°  C.  and 
cooling  one  cube  fast,  the  other  one  slow.  2.  Similar  treatment 
of  two  other  cubes  at  850°  C.  3.  Heating  for  five-minute  inter- 
vals in  a  strong  blast  and  cooling  for  alternate  five  minutes. 
4.  Alternately  heating  in  a  blast  for  five  minutes  and  quenching 
with  water  for  five  minutes. 

Professor  McCourt  in  summarizing  his  New  York  tests  made 
the  following  interesting  statements: 

"  At  550°  C.  (1022°  F.)  most  of  the  stones  stood  up  very  well. 
The  temperature  does  not  seem  to  have  been  high  enough  to 
cause  much  rupturing  of  the  samples,  either  upon  slow  or  fast 
cooling.  The  sandstones,  limestones,  marble  and  gneiss  were 
slightly  injured,  while  the  granites  seem  to  have  suffered  least. 

1  N.  Y.  State  Museum,  Bulletin  100,  1906;  also  N.  J.  Geol.  Surv.,  Ann.  Kept, 
for  1906,  p.  17,  1907;  see,  further,  Humphrey,  U.  S.  Geol.  Surv.,  Bull.  370,  1909. 


PLATE  XI.  —  Fire  tests  on  3  inch  cubes  of  sandstones  from  Pleasantdale,  N.  J. 
(After  W.  E.  McCourt.) 


77-   550°  C.,  slow  cooling. 
76.   850°  C.,  slow  cooling. 
179.   flame  test. 


78.   550°  C.,  fast  cooling. 

75.   850°  C.,  fast  cooling. 

148.   flame  and  water  test. 


57 


PLATE  XII.  —  Fire  tests  on  3  inch  cubes  of  limestone,  Newton,  N.  J. 
(After  W.  E.  McCourt.) 


216.  550°  C.,  slow  cooling. 
218.  850°  C.,  slow  cooling. 
2  20.  flame  test. 


217.  550°  C.,  fast  cooling. 
219.  850°  C.,  fast  cooling. 
221.  flame  and  water  test. 


59 


PLATE  XIII.— Fire  tests  of  3  inch  cubes  of  gneiss,  Mt.  Arlington,  N.  J. 
(After  W.  E.  McCourt.) 


228.  550°  C.,  slow  cooling. 
230.  850°  C.,  slow  cooling. 
232.  flame  test. 


229.  550°  C.,  fast  cooling. 
231.  850°  C.,  fast  cooling. 
233.  flame  and  water  test. 


61 


PLATE  XIV.  —  Fire  tests  of  3  inch  cubes  of  sandstone,  Warsaw,  N.  Y. 
(After  W.  E.  McCourt.) 

2.   550°  C.,  slow  cooling.  i.   550°  C.,  fast  cooling. 

4.   850°  C.,  slow  cooling.  3.   850°  C.,  fast  cooling. 

171.  flame  test.  139.   flame  and  water  test. 


PLATE  XV.  —  Fire  tests  of  3  inch  cubes  of  diabase,  Lambert vi lie,  N.  J. 
(After  W.  E.  McCourt.) 


255-  550°  C.,  slow  cooling. 
257.  850°  C.,  slow  cooling. 
259.  flame  test. 


256.  550°  C.,  fast  cooling. 
258.  850°  C.,  fast  cooling. 
260.  flame  and  water  test. 


PROPERTIES    OF    BUILDING    STONE  67 

"  The  temperature  of  a  severe  conflagration  would  probably 
be  higher  than  550°  C.,  but  there  would  be  buildings  outside  of 
the  direct  action  of  the  fire  which  might  not  be  subjected  to  this 
degree  of  heat  and  in  this  zone  the  stones  would  suffer  little 
injury.  The  sandstones  might  crack  somewhat;  but,  as  the 
cracking  seems  to  be  almost  entirely  along  the  bed,  the  stability 
of  the  structure  would  not  be  endangered,  provided  the  stone 
had  been  properly  set. 

"  The  gneiss  would  fail  badly,  especially  if  it  were  coarse- 
grained and  much  banded.  The  coarse-grained  granites  might 
suffer  to  some  extent.  These,  though  cracked  to  a  less  extent 
than  the  sandstones,  would  suffer  more  damage  and  possibly 
disintegrate  if  the  heat  were  long  continued,  because  the  irregular 
cracks,  intensified  by  the  crushing  and  shearing  forces  on  the 
stone  incident  to  its  position  in  the  structure,  would  tend  to  break 
it  down.  The  limestones  and  marble  would  be  little  injured. 

"  The  temperature  of  850°  C.  (1562°  F.)  represents  the 
probable  degree  of  heat  reached  in  a  conflagration,  though 
undoubtedly  it  exceeds  that  in  some  cases.  At  this  temperature 
we  find  that  the  stones  behave  somewhat  differently  than  at  the 
lower  temperature.  All  the  cubes  tested  were  injured  to  some 
degree,  but  among  themselves  they  vary  widely  in  the  extent  of 
the  damage. 

"  All  the  igneous  rocks  and  the  gneiss  at  850°  C.  suffered 
injury  in  varying  degrees  and  in  various  ways.  The  coarse- 
grained granites  were  damaged  the  most  by  cracking  very  ir- 
regularly around  the  individual  mineral  constituents.  Naturally, 
such  cracking  of  the  stone  in  a  building  might  cause  the  walls  to 
crumble.  The  cracking  is  due,  possibly,  to  the  coarseness  of 
texture  and  the  differences  in  the  coefficients  of  expansion  of  the 
various  mineral  constituents.  Some  minerals  expand  more  than 
others  and  the  strains  occasioned  thereby  will  tend  to  rupture 
the  stone  more  than  if  the  mineral  composition  is  simpler. 
This  rupturing  will  be  greater,  too,  if  the  rock  be  coarser  in 
texture.  For  example,  a  granite  containing  much  plagioclase 
would  be  more  apt  to  break  into  pieces  than  one  with  little 
plagioclase  for  the  reason  that  this  mineral  expands  in  one 
direction  and  contracts  in  another,  and  this  would  set  up  stresses 
of  greater  proportion  than  would  be  occasioned  in  a  stone  con- 
taining little  of  this  mineral In  the  gneisses  the  injury 

seems  to  be  controlled  by  the  same  factors  as  in  the  granites,  but 
there  comes  in  here  the  added  factor  of  banding.  Those  which 
are  made  up  of  many  bands  would  be  damaged  more  severely 
than  those  in  which  the  banding  is  slight. 


68  BUILDING   STONES   AND   CLAY-PRODUCTS 

k'  All  the  sandstones  which  were  tested  are  fine-grained  and 
rather  compact.  All  suffered  some  injury,  though,  in  most  cases, 
the  cracking  was  along  the  lamination  planes.  In  some  cubes, 
however,  transverse  cracks  were  also  developed. 

"  The  variety  of  samples  was  not  great  enough  to  warrant  any 
conclusive  evidence  toward  a  determination  of  the  controlling 
factors.  It  would  seem,  however,  that  the  more  compact  and 
hard  the  stone  is  the  better  will  it  resist  extreme  heat.  The 
following  relation  of  the  percentage  of  absorption  to  the  effect 
of  the  heat  is  interesting.  In  a  general  way  the  greater  the 
absorption,  the  greater  the  effect  of  the  heat.  A  very  porous 
sandstone  will  be  reduced  to  sand  and  a  stone  in  which  the  cement 
is  largely  limonite  or  clay  will  suffer  more  than  one  held  together 
by  silica  or  lime  carbonate. 

"  The  limestones,  up  to  the  point  where  calcination  begins 
(6oo°-8oo°  C.),  were  little  injured,  but  above  that  point  they 
failed  badly,  owing  to  the  crumbling  caused  by  the  flaking  of 
the  quicklime.  The  purer  the  stone,  the  more  will  it  crumble. 
The  marble  behaves  similarly  to  the  limestone;  but,  because  of 
the  coarseness  of  the  texture,  also  cracks  considerably.  As  has 
been  mentioned  before,  both  the  limestone  and  marble  on  sudden 
cooling  seem  to  flake  off  less  than  on  slow  cooling. 

"  The  flame  tests  can  not  be  considered  as  indicative  of  the 
probable  effect  of  a  conflagration  upon  the  general  body  of  the 
stone  in  a  building,  but  rather  as  an  indication  of  the  effect  upon 
projecting  cornices,  lintels,  pillars,  carving  and  all  thin  edges  of 
stonework.  All  the  stones  were  damaged  to  some  extent.  The 
limestones  were,  as  a  whole,  comparatively  little  injured,  while 
the  marble  was  badly  damaged.  The  tendency  seems  to  be  for 
the  stone  to  split  off  in  shells  around  the  point  where  the  greatest 
heat  strikes  the  stone.  The  temperature  of  the  flame  probably 
did  not  exceed  700°  C.,  so  it  is  safe  to  say  that  in  a  conflagration 
all  carved  stone  and  thin  edges  would  suffer.  However,  outside 
of  the  intense  heat,  the  limestones  would  act  best,  while  the  other 
stones  would  be  affected  in  the  order:  sandstone,  granite,  gneiss 
and  marble. 

"  After  having  been  heated  to  850°  C.,  most  of  the  stones,  as 
observed  by  Buckley,  emit  a  characteristic  ring  when  struck  with 
metal  and  when  scratched  emit  a  sound  similar  to  that  of  a  soft 
burned  brick.  It  will  be  noted  that  in  those  stones  in  which 
iron  is  present  in  a  ferrous  condition  the  color  was  changed  to 
a  brownish  tinge  owing  to  the  change  of  the  iron  to  a  ferric  state. 
If  the  temperature  does  not  exceed  550°  C.,  all  the  stones  will 
stand  up  very  well,  but  at  the  temperature  which  is  probable  in 


PROPERTIES   OF    BUILDING    STONE 


69 


a  conflagration,  in  a  general  way,  the  finer  grained  and  more 
compact  the  stone  and  the  simpler  in  mineralogic  composition 
the  better  will  it  resist  the  effect  of  the  extreme  heat.  The  order, 
then,  of  the  refractoriness  of  the  New  York  stones  which  were 
tested  might  be  placed  as  sandstone,  fine-grained  granite,  lime- 
stone, coarse-grained  granite,  gneiss  and  marble." 

Expansion  and  Contraction  of  Building  Stones.  Building 
stones  expand  when  heated  and  contract  when  cooled,  but  do  not 
return  to  their  original  length.  This  slight  increase  in  size  is 
known  as  the  "permanent  swelling."  The  determination  of  this 
change  in  volume  has  a  twofold  value,  as  it  permits  the  making 
of  proper  allowance  for  expansion  in  walls,  and  also  because  it 
may  weaken  the  stone  somewhat. 

The  following  averages  are  based  on  experiments  made  at 
the  Watertown  arsenal,1  the  permanent  swelling  being  for  a  bar 
20  inches  long,  heated  and  cooled  through  a  range  of  temperature 
from  32°  F.  to  212°  F. 

Inch. 

Granite o .  004 

Marble o .  009 

Limestone o .  007 

Sandstone o .  0047 

The  accompanying  table  gives  the  coefficients  of  expansion  of 
a  number  of  stones  as  determined  in  a  water  bath:2 

COEFFICIENTS  OF  EXPANSION  OF  STONES,  AS  DETERMINED 
IN  WATER  BATHS. 


Name. 

Location. 

Original 
gaged 
length 
in  air. 

Temperature. 

Coefficient 
of 
expansion. 

Hot. 

Cold. 

Differ- 
ence. 

Differ- 
ence in 
length. 

Buff  oolitic  limestone.  .  . 
Limestone 

Bedford,  Ind  
Indiana 

ins. 
20.0033 
20.0084 
19.0989 
20.0061 
20.0034 
19.0912 
20.0019 
19-9954 
20.0052 
20.0023 
19-9951 
19.9303 

deg. 
i?8 
177 
203 
189.5 
183 
180 
183 
194 
192 
183 
199 
181 

deg. 
33-5 
33-5 
34 
33-5 
33-5 
33-5 
33-5 
34 
33-5 
33-5 
33-5 
33-5 

deg. 
144-5 
143-5 
169 
156 
149-5 
146.5 
149-5 
160 
158.5 
149-5 
165.5 
147-5 

ins. 
0.0109 
0.0108 

O.OI22 

0.0175 
0.0152 
0.0154 
0.0186 
0.0158 
0.0189 

0.0122 
0.0126 
O.009I 

0.00000375 
o  .  00000376 
0.00000361 
0.00000562 
0.00000501 
0.00000526 
0.00000622 
0.00000500 
0.00000596 
0.00000408 
0.00000381 
0.00000311 

Marble  
Marble 

Vermont  
Lee,  Mass 

Red  sandstone  
Red  sandstone  
Sandstone 

Maryland  
Portland,  Conn.. 
Ohio  
Monson,  Me  
New  York... 
Milford,  Mass... 
Quincy,  Mass  
Rockport,  Mass.. 

Slate  

Bluestone   . 

Granite 

Granite  

Granite 

1  Report  on  tests  of  metals,  etc.,  at  Watertovm  Arsenal,  U.S.  War  Dept., 
1895,  pp.  322-23. 

2  Report  on  Tests  of  Metals,  etc.,  U.  S.  War  Dept.,  1890. 


70  BUILDING  STONES  AND   CLAY-PRODUCTS 

Abrasive  Resistance.  The  abrasive  resistance  of  a  stone  de- 
pends in  part  on  the  state  of  aggregation  of  the  mineral  particles 
and  in  part  on  their  individual  hardness.  Some  stones  wear 
very  unevenly  because  of  their  irregularity  of  hardness,  and 
such  may  be  less  desirable  than  those  which  are  uniformly  soft. 

Merrill1  states  that  a  " serpentinous  steatite"  used  many  years 
ago  for  steps  and  sills  in  Philadelphia  wore  very  unevenly,  owing 
to  the  superior  hardness  of  the  serpentine  over  the  steatite, 
causing  the  former  in  time  to  stand  out  like  knots  in  decaying 
logs." 

A  test  to  determine  the  abrasive  resistance  should  be  made  on 
those  stones  which  are  used  for  paving,  steps,  or  flooring,  in 
which  position  they  are  subjected  to  rubbing  action.  It  is  also 
of  importance  if  the  stone  is  placed  in  a  situation  where  it  will 
be  subjected  to  the  attacks  of  wind-blown  sand  or  the  rubbing 
action  of  running  water  carrying  sand. 

Several  methods  for  determining  the  abrasive  resistance  of 
stone  have  been  suggested,  but  none  universally  adopted. 

A  common  method  consists  in  laying  the  stone  to  be  tested  on 
a  grinding  table,  weighting  it  down,  and  applying  emery  or  some 
other  abrasive  at  a  given  rate  while  the  table  revolves.  The 
objections  to  this  method  are  that  one  cannot  be  sure  that  the 
abrasive  is  being  fed  at  a  uniform  rate  or  that  all  of  it  passes 
under  the  test  piece. 

Gary2  endeavored  to  perfect  the  test  by  cutting  slabs  of  50 
square  centimeters'  surface  parallel  with  the  bedding.  These 
were  held  down  with  a  30-kilogram  weight  and  placed  about 
22  centimeters  from  the  center  of  the  circular  rubbing  plate. 
At  one-minute  intervals,  20  grams  of  Naxos  emery  of  a  certain 
size  were  strewn  on  the  table.  The  abrasive  and  abraded  rock 
remained  on  the  table  until  the  completion  of  no  revolutions, 
which  consumed  about  five  minutes.  No  water  was  used.  The 
loss  of  weight  of  the  stone  indicated  the  amount  of  abrasion. 

Another  experimenter,  Hannover,  tried  to  improve  on  this 
method  by  using  sandpaper,  which  held  the  abrasive  grains  in 
place. 

1  "Stones  for  Building  and  Decoration,"  p.  460. 

2  Baumaterialienkunde,  II,  p.  n,  1897-98. 


n  tKoth, -nburg  a  S.I 


PLATE  XVI.  —  Results  of  abrasion  test  with  sand  blast. 
(After  Gary,  Baumaterialienkunde.) 


PROPERTIES    OF    BUILDING    STONE 


73 


Owing  to  the  difficulty  of  maintaining  uniform  conditions,  the 
test  is  an  unsatisfactory  one  and  of  use  mainly  where  compara- 
tive results  are  desired  and  several  pieces  tested  at  the  same  time. 

Gary1  has  also  devised  a  sand-blast  process  which  consists  in 
forcing  sand  through  a  6-centimeter  diameter  opening,  under  a 
dry-steam  pressure  of  3  atmospheres,  for  2  minutes.  The  stone 
to  be  tested  is  held  immediately  over  the  opening  (Plate  XVI). 

The  following  figures  give  the  results  obtained  by  him  with 
both  methods: 

ABRASION  TESTS  MADE   BY  GARY. 


Abrasion  on  rubbing  table. 

Abrasion  with  sand  blast. 

Nam 

Normal  to  bedding. 

Parallel  to  bedding. 

Surface. 

Average 
loss. 

Abrasion 
loss  ratio 
of  c.  cm. 

Average 
loss. 

Abrasion 
loss  ratio 
of  c.  cm. 

Average 
loss. 

Abrasion 
loss  ratio 
of  c.  cm. 

sq.  cm. 

c.  cm. 

sq.  cm. 

c.  cm. 

sq.  cm. 

c.  cm. 

sq.  cm. 

Basalt 

ero 

r   4 

O.  II 

I  .  70 

O.o6 

I    8l 

O.o6 

Basalt  lava. 

o 

49 

0   '  T" 
9.6 

o.  20 

6.01 

O.  21 

7-06 

0.25 

Granite  

49 

5-1 

0.  10 

2  .64 

O.O9 

3.78 

0.13 

Gneiss  

48 

9-6 

o.  20 

4.01 

0.14 

3-26 

O.I2 

Porphyry.  .  . 

49 

8-5 

0.17 

3-29 

O.  12 

2.58 

O.O9 

Gray  wacke  . 

50 

10.8 

0.22 

4.24 

0-15 

4.16 

0-15 

Sandstone.  . 

50 

18.4 

0-37 

11.15 

0-39 

8.42 

0.30 

Schist  

50 

29.7 

o-59 

8.02 

0.28 

5-9° 

0.21 

The  sand-blast  treatment  not  only  tests  the  abrasive  resistance 
but  also  brings  out  irregularities  in  the  hardness. 

Discoloration.  Some  building  stones  discolor  on  exposure  to 
the  atmosphere,  the  alteration  involving  a  chemical  change 
within  the  rock,  caused  by  atmospheric  action.  The  change  in 
tone  or  color  is  usually  slow. 

In  order  to  determine  whether  a  stone  contains  any  minerals 
likely  to  discolor  the  rock,  a  piece  of  fresh  rock  is  immersed  in  a 
stream  of  carbon  dioxide  for  20  minutes  and  then  placed  in  an 
atmosphere  of  that  gas  for  24  hours.  A  second  piece  is  placed 
in  pure  oxygen  over  night  and  exposed  for  30  minutes  to  a  tem- 
perature of  150°  C.  Any  discoloration  caused  by  carbonization 

1  Baumaterialienkunde,  X,  p.  133,  1905. 


74  BUILDING   STONES  AND   CLAY-PRODUCTS 

or  oxidation  of  any  mineral  in  the  rock  is  sure  to  become 
noticeable. 

Another  method  consists  in  placing  the  stone  to  be  tested  on 
a  glass  shelf,  in  a  covered  glass  jar  containing  hydrochloric  acid. 
Alongside  of  the  specimen  are  placed  two  open  bottles,  one 
containing  hydrochloric  acid  and  manganese  dioxide;  the  other, 
strong  nitric  acid. 

The  chlorine  and  acid  fumes  rising  and  filling  the  chamber 
form  an  extremely  corrosive  and  oxidizing  mixture  and  quickly 
attack  any  oxidizable  compounds  where  such  exist. 

The  test  piece  is  left  in  this  atmosphere  for  several  weeks  and 
any  change  of  color  noted. 

Effect  of  Sulphurous  Acid  Gas  and  Dilute  Sulphuric  Acid.  The 
stones  most  affected  by  this  treatment  are  limestones,  which 
contain  lime  or  magnesium  carbonates.  Sandstones  with  cal- 
careous cement  may  also  be  attacked. 

These  acid  gases  mentioned  above  may  be  discharged  into  the 
atmosphere  from  chimneys  or  other  sources  and  carried  to  the 
surface  of  the  stone  by  moisture,  or  they  may  originate  in  the 
stone  itself  by  the  decomposition  of  pyrite  or  marcasite  if  these 
minerals  are  present. 

While  their  action  is  slow  it  is  nevertheless  not  to  be  overlooked. 

The  resistance  of  a  rock  to  sulphurous  acid  gas  is  sometimes 
tested  by  placing  carefully  dried  two-inch  cubes  in  a  sealed 
wide-mouthed  bottle  kept  at  a  temperature  of  110°  C.  Water 
in  the  jar  keeps  the  air  moist,  and  sulphur  dioxide  gas  is  fed  into 
it  in  sufficient  quantity  to  saturate  the  atmosphere.  After 
30  or  40  days'  exposure  to  these  conditions  the  samples  are  re- 
moved, washed,  thoroughly  dried  and  weighed,  the  loss  of 
weight,  if  any,  showing  the  degree  to  which  the  stone  has  been 
attacked  by  the  gas. 

Dolomites  may  swell  and  crumble,  because  of  the  change  of 
magnesium  carbonate  to  magnesium  sulphate. 

Such  a  test  is  more  severe  than  a  stone  would  be  subjected  to 
in  actual  use. 

Effect  of  Carbonic  Acid  Gas.  This  is  most  effective  when  it 
attacks  calcareous  rocks.  Others  may  be  but  little  affected. 


PROPERTIES   OF    BUILDING    STONE  75 

The  test  may  be  carried  out  by  placing  weighed  specimens 
dried  at  110°  C.  in  a  large  bottle.  In  this  there  is  also  a  small 
vessel  of  water  to  keep  the  atmosphere  moist.  Pass  carbon 
dioxide  gas  into  the  bottle  until  it  displaces  all  the  air  present. 
Cover  the  bottle,  allow  to  stand  for  six  weeks,  taking  care  to 
replenish  the  carbon  dioxide  about  twice  a  week.  At  the  end  of 
the  period  mentioned,  remove  the  stone,  wash  with  distilled 
water,  dry  and  weigh.  The  loss  in  weight  indicates  the  extent 
to  which  it  has  been  attacked. 

Another  way  of  making  the  test  is  to  suspend  the  stone 
in  water  through  which  carbon  dioxide  gas  is  allowed  to 
bubble. 

Chemical  Composition  of  Building  Stones.  Much  money  is 
spent  on  the  analysis  of  building  stones,  but  the  returns  are  slight. 
This  is  because  few  interpretations  can  be  made  from  such  an 
analysis,  for  it  throws  no  light  on  most  of  the  properties  which 
have  been  discussed  in  the  preceding  pages. 

It  is  true  that  an  analysis  may  show  the  difference  between  a 
limestone  and  a  dolomite,  but  a  simple  test  will  do  this.  It  may 
indicate  whether  a  sandstone  is  pure  or  impure,  but  this  too  can 
be  told  with  fair  accuracy  on  inspection.  It  might  indicate 
pyrite  in  a  rock,  but  if  the  former  is  present  in  injurious  amounts, 
its  occurrence  can  usually  be  detected  with  the  naked  eye  or 
hand  lens.  So,  on  the  whole,  the  chemical  analysis  is  not  of 
much  value  for  commercial  purposes  so  far  as  building  stones  are 
concerned. 

WEATHERING  AND  DECAY  OF  BUILDING  STONES. 

Under  this  term  are  included  the  physical  and  chemical  changes 
which  a  stone  undergoes  when  exposed  to  the  weather.  Some 
building  stones  are  but  little  affected  under  any  climatic  condi- 
tions and  are,  therefore,  long  lived,  while  others  disintegrate 
most  rapidly. 

All  stones  are,  therefore,  not  equally  well  adapted  to  any  kind 
of  conditions,  and  since  architects  sometimes  fail  to  recognize 
this  fact,  many  a  fine  and  expensive  structure  at  the  present  day 
presents  a  most  unsightly  appearance. 


76  BUILDING  STONES  AND   CLAY-PRODUCTS 

Nowhere  are  the  mistakes  of  this  sort  so  evident  as  in  the 
severe  climate  of  our  northeastern  states,  for  moisture  combined 
with  heat  and  cold  have  wrought  much  havoc.  The  cracked 
and  scaling  fronts  of  brownstones  in  many  eastern  cities  stand 
as  a  monument  to  the  poor  selection  and  improper  placing  of 
building  stones. 

While  exposure  to  the  weather  may  bring  about  noticeable 
changes  in  a  stone,  still  it  may  be  pointed  out  that  these  do  not 
invariably  indicate  a  weakening  of  the  rock.  The  Berea,  Ohio, 
sandstone  is  a  noticeable  example  of  this.  Here  the  finely 
divided  pyrite  is  very  evenly  distributed  through  the  stone,  and 
its  change  to  limonite  on  exposure  to  the  weathering  results 
only  in  a  change  of  color  without  loss  of  strength. 

In  judging  the  durability  of  a  building  stone,  climatic  condi- 
tions should  be  considered.  Thus,  the  excellent  state  of  preser- 
vation in  which  we  find  the  obelisks  of  Egypt  or  the  marble 
monuments  of  Rome  is  not  due  to  any  inherent  qualities  of  the 
stone,  but  to  the  mild  climate  in  which  they  have  stood. 

The  Egyptian  obelisk  brought  to  New  York  City  and  set  up 
in  Central  Park  showed  such  rapid  disintegration  that  it  became 
necessary  to  cover  it  with  a  protective  coating. 

Stones  may  be  broken  down  by  the  weather  in  two  ways. 
The  first  of  these  is  by  physical  means  and  is  known  as  disinte- 
gration; the  second,  by  chemical  processes,  known  as  decomposi- 
tion. Either  of  these  alone  may  work  the  ruin  of  the  stone,  but 
they  are  more  apt  to  work  jointly,  although  the  one  or  the  other 
may  predominate. 

The  two  classes  of  processes  will  next  be  discussed  in  more 

detail. 

DISINTEGRATION. 

Temperature  Changes,  or  Heat  and  Cold.  Stones  expand  when 
heated  and  contract  when  cooled.  They  are,  moreover,  poor 
conductors  of  heat,  so  that  one  side  of  a  stone  might  be  highly 
heated  while  the  other  side  is  still  cool.  This  alone  would  pro- 
duce an  uneven  expansion,  tending  to  crack  the  mass. 

Since  different  minerals  have  a  different  rate  of  expansion  it  is 
easily  understood  that  continually  repeated  heating  and  cooling 


PLATE  XVII,  Fig.  i.  —  Weathering  of  red  sandstone,  Denver,  Colo. 
(Photo  by  R.  D.  George.) 


PLATE  XVII,  Fig.  2.  —  Weathered  sandstone,  second  story,  County  Court  House, 
Denver,  Colo.     (Photo  by  R.  D.  George.) 

77 


PROPERTIES   OF    BUILDING    STONE  79 

may  set  up  a  working  within  the  mass  that  would  tend  to  eventu- 
ally loosen  it  up. 

Bartlett1  has  determined  that  the  expansion  of  different  stones, 
for  each  degree  of  Fahrenheit,  is  as  follows : 

Inch. 

Granite o .  000004825 

Marble o .  000005668 

Sandstone o .  000009532 

Taking  the  case  of  granite,  we  find  that  for  a  change  of  100°  F. 
and  100  feet  of  granite  it  would  amount  to  about  one-twentieth 
of  an  inch. 

Expansion  caused  by  Freezing.  If  a  stone  is  porous  and  the 
pores  are  filled  with  water,  far  greater  damage  may  result  by 
changes  of  temperature,  for  the  reason  that  water  in  freezing 
expands  one-tenth.  Now,  if  the  pores  are  so  filled  with  water 
which  has  no  chance  to  escape,  the  internal  pressure  exerted  by 
it  will  be  very  great,  amounting  to  a  little  less  than  150  tons  per 
square  foot,  which  a  stone  may  not  be  able  to  resist. 

Much  misconception  exists  concerning  the  frost  resistance  of 
stones.  If  the  pores  are  exceedingly  small  (sub-capillary),  the 
water  may  have  no  chance  to  escape,  while  if  large,  the  water 
drains  off  readily,  and  no  damage  results.  Again,  incomplete 
saturation  of  the  rock  leaves  room  for  the  water  to  expand  in 
freezing  without  damaging  the  stone. 

Two  stones  of  equal  porosity  may  differ  in  their  frost  resistance, 
and  the  one  whose  pores  are  quite  minute  will  be  more  likely  to 
suffer.  Two  stones  having  pores  of  equal  size  will  vary  in  their 
resistance  inversely  as  the  amount  of  pore  space. 

As  pointed  out  by  Buckley,  the  amount  of  water  which  the 
pores  contain  at  a  given  time  depends  (i)  upon  the  amount  of 
water  initially  absorbed,  (2)  the  time  that  has  elapsed  since 
the  water  was  absorbed,  (3)  the  size  of  the  pores,  (4)  the  posi- 
tion of  the  stone,  and  (5)  the  condition  of  the  atmosphere. 

Much  danger  may  also  result  from  the  accumulation  of  water 
in  joint  or  bedding  planes.  This  is  especially  pronounced  if  the 
stone  is  set  on  edge,  for  the  water  freezing  in  the  parting  planes 
pries  off  scales  and  chips  at  a  rapid  rate. 

1  Amer.  Jour.  Sci.,  XXII,  1832,  p.  136. 


8o  BUILDING  STONES  AND   CLAY-PRODUCTS 

Abrasive  Action.  Wind-blown  sand  is  a  common  abrading 
agent  in  some  regions,  and  in  some  cases,  as  those  of  tombstones 
in  cemeteries,  has  removed  the  polish  and  even  obliterated  the 
lettering  on  monuments. 

Stone  which  is  used  for  sidewalks,  flooring,  stair-treads,  etc., 
is  especially  exposed  to  the  rubbing  action  of  sand,  ground  against 
the  surface  by  shuffling  feet. 

Much  variation  exists  in  this  direction,  some  stones  being  but 
little  affected,  others  becoming  badly  worn  in  a  short  time. 

Plant  Action.  The  action  of  plants  is  not  altogether  a  physi- 
cal one.  On  the  outcrop,  plant  roots  often  penetrate  the  cracks 
and  crevices  of  a  stone  and,  as  they  grow  and  expand,  exert 
sufficient  pressure  to  pry  off  fragments,  but  this  does  not  occur 
in  buildings.  There  the  rootlets  of  vines  may  penetrate  the 
pores  of  an  open  rock,  but  they  probably  exert  no  physical  force. 

They  may,  however,  aid  in  the  decomposition  of  the  rock  by 
the  formation  of  organic  acids  produced  during  decay.  More- 
over, they  attract  moisture  to  the  stone. 

Careless  Methods  of  Extraction  and  Working.  A  stone  may  be 
weakened  and  rendered  more  vulnerable  to  the  attacks  of  the 
weathering  agents  by  improper  methods  of  quarrying  and  work- 
ing. 

The  use  of  heavy  charges  of  powder  or  dynamite  not  only 
destroys  a  large  quantity  of  stone,  but  also  develops  minute 
cracks  —  incipient  joints  —  which  permit  the  more  ready  en- 
trance of  water  into  the  stone,  with  increased  danger  from 
freezing  and  thawing.  The  continuous  striking  of  a  stone  with 
hammer  and  chisel  in  splitting  or  dressing  it  is  likewise  a  possi- 
ble cause  of  damage. 

Injuries  in  quarrying  may  be  avoided  by  taking  advantage  of 
the  natural  joints  as  much  as  possible,  by  the  Knox  system  of 
quarrying,  in  which  small  charges  of  powder  are  properly  dis- 
tributed, or  by  the  channeling  system  now  much  used  in  lime- 
stone, sandstone,  marble  and  even  slate  quarrying. 

Many  stones  should  not  be  quarried  in  freezing  weather, 
because  the  exposure  may  cause  the  quarry  water  in  their  pores 
to  freeze. 


PROPERTIES   OF    BUILDING    STONE  81 

The  life  of  a  stone  depends  to  a  limited  extent  on  the  method 
of  dressing.  The  polished  surface  sheds  water  more  easily  than 
a  rough  one.  A  hammer-dressed  rock,  like  sandstone,  may  dis- 
integrate more  rapidly  than  a  sawed  one. 

Finally,  position  when  in  use  is  a  matter  not  to  be  overlooked. 
Many  stones  of  stratified  or  schistose  character  can  be  dressed 
more  easily  and  more  smoothly  along  the  bed.  On  this  account 
they  are  set  in  the  wall  on  edge.  This  permits  the  rock  to  scale 
off  more  easily  than  if  set  on  bed,  for  the  pressure  of  the  overlying 
blocks  in  the  wall  will  resist  the  upward  pressure  of  the  freezing 
water,  and  it  will  exert  itself  parallel  with  the  stratification. 

Of  course,  some  stones  are  so  strongly  knit  together  and  the 
schistosity  or  stratification  so  slightly  developed  that  they  can 
be  safely  set  on  edge. 

DECOMPOSITION. 

The  chemical  processes  working  to  break  down  the  stone  usu- 
ally operate  with  slowness,  although  one  at  times  finds  marked 
exceptions.  Important  agents  of  decomposition  are  water, 
oxygen  and  acids.  In  most  cases  the  changes  wrought  by  these 
agents  are  so  slow  that  they  do  not  often  affect  the  durability  of 
the  stone  after  it  is  set  in  the  building;  indeed,  the  limestones, 
dolomites  and  marbles  are  about  the  only  ones  in  which 
decomposition  advances  at  a  sufficiently  rapid  rate  to  be 
noticeable. 

Water  may  act  by  direct  attack  on  the  rock  itself,  or  it  may 
serve  as  a  carrier  of  other  injurious  substances. 

Pure  water  shows  but  little  solvent  action,  but  if  contaminated 
by  the  presence  of  sulphuric,  sulphurous,  carbonic  or  organic 
acids  its  dissolving  power  is  noticeably  increased.  Its  work  in 
this  manner  is  most  noticeable  in  limestones.  Water  in  con- 
tact with  these  dissolves  out  small  quantities  here  and  there 
throughout  the  stone,  and  by  thus  removing  more  or  less  of  its 
cement  or  even  portions  of  the  mineral  grains  themselves  greatly 
weakens  it.  This  effect  is  more  pronounced  in  limestones  than 
in  dolomites.  Sandstones  having  a  calcareous  cement  may  be 
similarly  affected. 


82  BUILDING  STONES  AND   CLAY-PRODUCTS 

In  rocks  like  granite  the  decomposition  of  minerals  like 
feldspar,  mica,  or  hornblende  is  a  more  complex  process, 
involving  more  than  simple  solution.  All  of  these  minerals 
break  down  slowly  to  a  more  or  less  clayey  mass,  and  if  they 
contain  iron,  the  latter  is  set  free  in  the  form  of  limonite 
(hydrous  iron  oxide),  which  develops  a  rusty  stain.  The 
changes  in  these  silicates  are  usually  so  slow  as  to  be  almost 
negligible  in  building  stones. 

Where  a  rock  like  granite  has,  however,  been  exposed  to  the 
attacks  of  the  weathering  agents  for  many  centuries,  the  upper 
portion  of  the  mass  may  have  become  broken  down  to  a  plastic, 
often  iron-stained  clay.  This  residual  clay  forms  a  mantle  over- 
lying the  parent  rock  and  grades  down  into  it.  In  the  Southern 
Atlantic  states,  for  example,  where  this  overlying  clay  has  not 
been  removed  by  glacial  erosion,  as  it  has  been  in  the  Northern 
ones,  it  is  sometimes  necessary  for  the  quarryman  to  strip  off  con- 
siderable material  in  order  to  reach  sound  rock.  This  will  not  be 
found  at  the  same  depths  in  all  parts  of  the  quarry,  for  where 
the  vertical  joints  are  more  numerous  the  rotted  rock  is  usually 
found  to  a  greater  depth. 

The  oxidation  of  pyrite  often  leads  to  troublesome  results. 
This  mineral,  on  exposure  to  moisture  and  air,  changes  to  limo- 
nite, or  rust. 

If  the  sulphide  is  scattered  through  the  stone  in  small  grains 
no  harm  may  result,  as  the  change  in  color  does  not  necessarily 
weaken  the  stone;  on  the  contrary  it  may  improve  its  looks. 
Furthermore,  the  deposition  of  this  iron  oxide  around  the  grains 
may  cement  them  more  firmly  together.  In  most  rocks,  however, 
the  change  in  the  pyrite  leads  to  unsightly  staining  of  the  stone, 
and  one  containing  any  quantity  of  it  in  visible  grains  should  be 
avoided.  It  may  work  further  harm  in  limestones,  because 
during  its  decomposition  small  quantities  of  sulphurous  or  sul- 
phuric acids  are  formed  which  may  attack  some  of  the  minerals 
of  the  stone. 

Other  iron  compounds,  like  ferrous  carbonate,  or  magnetite, 
may  undergo  an  oxidizing  action  and,  if  abundant,  give  the  rock 
a  rusty  tint. 


PLATE  XVIII.  —  Scum  of  soluble  salts,  which  has  caused  surface  disintegration 
of  sandstone.     (After  Kaiser,  Neues  Jahrb.  Min.,  1907,  II.) 


PROPERTIES   OF    BUILDING    STONE  85 

Sulphurous  and  Sulphuric  Acids.  These  may  not  only  be 
produced  by  the  weathering  of  pyrite  as  mentioned  above,  but 
may  also  be  derived  from  the  atmosphere,  especially  in  those 
districts  where  acid  fumes  are  discharged  into  the  air  from  the 
stacks  of  factories,  smelters,  etc. 

These  acids  attack  the  rocks,  especially  those  containing  car- 
bonate compounds  like  limestones  and  dolomites  and  marbles. 
This  results  in  these  carbonates  being  converted  into  sulphates, 
a  transformation  involving  change  of  volume.  The  sulphates 
thus  formed  may  either  lodge  in  the  pores  of  the  rock,  or  they 
may  be  brought  to  the  surface  by  evaporating  water  and  there 
form  a  scum. 

An  interesting  case  has  been  described  by  E.  Kaiser,1  of  the 
disintegration  by  sulphates  of  the  sandstone  in  the  Cologne 
Cathedral  (Plate  XVIII): 

The  weathered  stones,  which  were  certain  ones  used  between  1842  and  1868, 
show  externally  an  apparently  unaltered  scale,  while  between  this  and  the  solid 
stone  within  is  a  white  layer  of  water-soluble  salts.  Sometimes  there  are  several 
alternations  of  these  layers.  The  cement  of  the  fresh  stone  is  a  mixture  of  kaolin, 
barite  and  dolomite.  No  other  sulphur  mineral  than  barite  is  present  in  the 
stone.  In  the  quarry  the  weathering  consists  in  a  solution  of  the  calcium  and 
magnesium  components  of  the  dolomite  with  deposition  of  the  iron  as  hydrated 
ferric  oxide.  On  the  cathedral,  however,  the  white  layers  are  composed  of  sul- 
phates of  calcium  and  magnesium.  The  conclusion  is  inevitable  that  the  sulphur 
is  derived  from  the  city  smoke  and  that  the  process  of  disintegration  can  be  halted 
only  by  the  application  of  an  impervious  coating.  Examination  of  structures  in 
other  parts  of  Germany,  where  the  same  stone  has  been  used,  shows  a  similar 
condition,  the  degree  of  attack  varying  with  the  relative  production  of  smoke 
gases  and  the  exposure  of  the  structural  material  to  these  gases. 

Carbon  dioxide  in  solution  may  also  exert  a  solvent  action  on 
calcareous  rocks.  Its  effect  on  other  kinds  is  scarcely  noticeable 
in  the  building. 

Organic  acids,  though  playing  an  important  role  in  the 
weathering  of  rocks  in  the  field,  exert  but  little  influence  on  the 
stone  in  the  wall. 

Hardening  of  Stone  on  Exposure.  All  quarrymen  are  familiar 
with  the  fact  that  many  stones  harden  on  exposure  to  the  at- 
mosphere, this  change  being  specially  noticeable  in  limestones 

1  Neues  Jahrb.  Min.  Geol.  Pal.,  1907,  II,  42-64 


86  BUILDING  STONES  AND   CLAY-PRODUCTS 

and  sandstones.     So  pronounced  is  this  change  that  some  stones 
are  more  easily  dressed  when  freshly  quarried  than  later. 

The  hardening  has  been  considered  by  several  investigators 
to  be  due  to  the  fact  that  the  water  in  the  pores  of  the  stone  - 
the  quarry  water  —  contains  a  small  quantity  of  dissolved 
mineral  matter,  which  it  deposits  in  the  pores  of  the  stone  on 
evaporation.  The  formation  of  this  additional  cement,  there- 
fore, serves  to  bind  the  stone  more  tightly  together.  This  cement- 
ing action,  of  course,  takes  place  on  or  close  to  the  surface,  thus 
forming  a  protecting  crust.  On  this  account  it  is  urged  by  some 
that  the  carving  of  a  stone  should  be  done  before  it  dries  out,  thus 
permitting  the  crust  to  form  on  the  carved  surface. 

The  weathering  qualities  of  the  different  classes  of  building 
stone  will  be  more  fully  discussed  under  their  respective  heads. 

Life  of  a  Building  Stone.  This  may  be  considered  as  the  length 
of  time  a  stone  will  stand  exposure  to  the  weather  without  show- 
ing signs  of  disintegration  or  decay.  Even  for  the  same  stone 
it  may  vary  with  location,  climate,  and  position  in  the  wall. 

The  following  table  was  compiled  some  years  ago  by  Dr.  A.  A. 
Julien,  from  observations  on  building  stones  in  New  York  City: 


Kind  of  stone. 


Coarse  brownstone 

Fine  laminated  brownstone 

Compact  brownstone 

Bluestone  (sandstone),  untried,  perhaps  centuries 

Ohio  sandstone  (best  siliceous  variety),  perhaps  from  one  to 
many  centuries. 

Coarse  f ossiliferous  limestone 

Fine  oolitic  (French)  limestone 

Marble,  coarse  dolomitic 

Marble,  fine  dolomitic 

Marble,  fine 

Granite ...  


Gneiss,  50  years  to  many  centuries. 


Life,  in  years. 


5  to    15 
20  to    50 

100  tO  200 


20  tO     40 

30  to    40 

40 

60  to  80 
50  to  ioo 
75  to  200 


There  is  no  weight  in  the  argument  that  Nature's  processes  are 
very  slow,  and  that  any  building  stone  will  last  for  several  genera- 
tions. This  is  not  so.  Any  large  city,  where  a  variety  of  stones 
are  used,  will  be  apt  to  show  cases  of  rapid  decay  if  the  climate 
is  at  all  severe. 


PROPERTIES    OF    BUILDING   STONE  87 

Merrill1  cites  the  case  of  a  coarse,  gray  Niagara  limestone  from 
Lockport,  New  York,  used  in  the  construction  of  the  Lenox 
Library  Building  in  New  York  City,  which  began  to  show  signs 
of  decay  even  before  the  structure  was  completed.  But  this 
extremely  rapid  rate  was  due  in  part  to  the  fact  that  the  stone 
was  laid  on  edge. 

A  case  which  came  under  the  writer's  observation  was  that  of 
the  polished  cipolino  marble  columns  on  the  front  of  St.  Bartholo- 
mew's Church  at  44th  Street  and  Madison  Avenue,  New  York 
City.  These  in  three  years  had  lost  their  polish  and  were  pitted 
and  flaked  to  such  a  degree  that  it  became  necessary  to  rerub 
the  surface  and  treat  it  with  a  preservative.  This  type  of  stone 
should  never  have  been  used  for  exterior  work  in  the  New  York 
climate. 

Pages  might  be  filled  quoting  examples  of  this  sort. 

Sap.  This  is  a  rusty  discoloration  produced  by  iron,  which  is 
often  found  in  those  portions  of  the  stone  bordering  joint  planes. 
It  is  noticed  especially  in  granites.  In  some  cases  it  is  due  to  the 
decomposition  of  iron-bearing  minerals  in  the  rock  by  surface 
waters ;  in  others  it  may  be  an  iron  stain  from  water  which  niters 
downward  along  the  joint  planes. 

LITERATURE  ON  BUILDING  STONES. 

As  the  architect  or  engineer  is  frequently  desirous  of  knowing 
what  the  important  printed  sources  of  information  on  building 
stones  are,  it  may  be  well  to  indicate  some  of  the  more  important 
publications,  all  of  which  have  been  drawn  upon  freely  in  the 
preparation  of  this  book.  These  are  grouped  below: 

GENERAL  WORKS. 

Merrill,  G.  P.     Stones  for  Building  and  Decoration,  New  York  (Wiley  & 

Sons) . 
McCourt,  W.  E.     N.  Y.  State  Museum  Bull.  100, 1906,  and  N.  J.  Geol.  Surv., 

Ann.  Rept.  1906.     (Valuable  papers  on  fire  tests.) 
Humphreys.     U.  S.  Geol.  Surv.,  Bull.  370,  1909.     (Fire  tests.) 
Brown,  W.  M.     Stone,  June,  1908.     (Preservation  methods.) 
Hermann,    O.     Steinbruchindustrie   und   Steinbruchgeologie,    Berlin,    1899. 

(Gebriider  Borntrager.) 

1  Stones  for  Building  and  Decoration,  3d  ed.,  p.  454. 


88  BUILDING  STONES  AND   CLAY-PRODUCTS 

Darras,  M.      Marbrerie,  Paris,  1912.      (Dunod.) 

Davies,  D.  C.  Slate  and  Slate  Quarrying,  London,  1899.  (Crosby, 
Lockwood  and  Son.) 

Foerster.      Baumaterialienkunde,  Leipzig,  1905.      (W.  Engelmann.) 

Pullen,  H.  W.  Handbook  of  Ancient  Roman  Marbles,  London,  1894. 
(John  Murray.) 

Renwick,  W.  G.  Marble  and  Marble  Working,  London,  1909.  (Lock- 
wood,  Crosby  and  Son.) 

Seipp,  H.  Wetterbestandigkeit  der  natiirlichen  Bausteine,  Jena,  1900. 
(H.  Costenoble.) 

SERIALS. 

Stone,  a  monthly  published  in  New  York  City. 
Baumaterialienkunde,  published  by  Stable  und  Friedel,  Stuttgart. 

Alabama:  SPECIAL  PAPERS' 

Smith.     Eng.  and  Min.  Jour.,  LXVI,  p.  398. 

Smith.     Min.  Resources  Ala.,  Ala.  Geol.  Surv.,  1904. 

Watson.     U.  S.  Geol.  Surv.,  Bull.  426,  1910.     (Granites.) 
Alaska: 

Wright.     U.  S.  Geol.  Surv.,  Bull.  345,  p.  116,  1908. 
Arizona: 

Anon.     Stone,  Aug.,  1911.     (Marbles.) 
Arkansas: 

Purdue.     Ark.  Geol.  Surv.,  1909.     (Slate.) 

Hopkins.     Ark.  Geol.  Surv.,  Ann.  Rept.  1890,  IV,  1893.     (Marbles.) 

Williams,  J.  F.    Ark.  Geol.  Surv.,  Ann.  Rept.  1890,  II,  1891.     (Igneous  rocks.) 
California: 

Aubury  and  others.     Calif.  State  Min.  Bur.,  Bull.  38,  1906.     (General.) 

Eckel.     U.  S.  Geol.  Surv.,  Bull.  225,  p.  417,  1904.     (Slate.) 
Colorado: 

Stone,  XI,  p.  213,  1895. 

Lakes,  Mines  and  Minerals,  XXII,  pp.  29  and  62,  1901. 
Connecticut: 

Dale.     U.  S.  Geol.  Surv.,  Bull.  484,  1911.     (Granites.) 
Georgia: 

McCallie.     Ga.  Geol.  Surv.,  Bull,  i,  2d  ed.,  1904.     (Marbles.) 

Watson.     Ibid,  Bull.  9~A,  1903.     (Granites  and  gneisses.) 

Watson.    U.  S.  Geol.  Surv.,  Bull.  426,  1910.     (Granites.) 
Indiana: 

Hopkins.    Ind.  Geol.  and  Nat.  Hist.  Surv.,  2oth  Ann.  Rept.,  p.  188,  1896. 

Siebenthal.     U.  S.  Geol.  Surv.,  i9th  Ann.  Rept.,  VI.,  p.  292,  1898.     (Bedford 
limestone.)     Also  32d  Ann.  Rept.,  1907,  p.  321.     (Limestone.) 

Thompson.     Ibid,  i7th  Ann.  Rept.,  p.  19,  1891.     (General.) 

Iowa: 

Beyer  and  Williams.     la.  Geol.  Surv.,  XVII,  p.  185,  1907.     (General.) 
Marston.     Ibid,  p.  54.     (Tests.) 


PROPERTIES    OF    BUILDING   STONE  89 

Kentucky: 

Gardiner.    U.  S.  Geol.  Surv.,  Bull.  430.     (Bowling  Green  limestone.) 

Maine: 

Dale.     U.  S.  Geol.  Surv.,  Bull.  313,  1907.     (Granite.) 

Maryland: 

Matthews.     Md.  Geol.  Surv.,  II,  p.  125,  1908. 

Watson.     U.  S.  Geol.  Surv.,  Bull.  426,  1910.     (Granites.) 

Massachusetts: 

Dale.     U.  S.  Geol.  Surv.,  Bull.  354,  1908.     (Granites.) 

Michigan: 

Benedict.     Stone,  XVII,  p.  153.     (Bayport  district.) 

Minnesota: 

Burchard.     U.  S.  Geol.  Surv.,  Bull.  430. 

Missouri: 

Buckley  and  Buehler.     Mo.  Bur,  Geol.  and  Mines,  II,  1904. 

Montana: 

Rowe.    Univ.  of  Mont.,  Bull.  50. 
New  Hampshire: 

Dale,  U.  S.  Geol.  Surv.,  Bull.  354, 1908.     (Granites.) 

New  Jersey: 

Lewis.     N.  J.  Geol.  Surv.,  Ann.  Rept.,  1908,  p.  53,  1909. 

New  York: 

Dale.     U.  S.  Geol.  Surv.,  Bull.  275.     (Slate.) 

Dickinson.     N.  Y.  State  Museum,  Bull.  61,  1903.     (Bluestone.) 

Smock.     Bull.  N.  Y.  State  Museum,  3. 
North  Carolina: 

Watson,  Laney  and  Merrill.     N.  C.  Geol.  Surv.,  Bull.  2,  1906. 

Watson.     U.  S.  Geol.  Surv.,  Bull.  426,  1910.     (Granites.) 

Ohio: 

Orton.     Ohio  Geol.  Surv.,  V.,  p.  578,  1884. 

Orton  and  Peppel.     Ohio  Geol.  Surv.,  4th  Series,  Bull.  4,  1906.     (Limestones.) 
Oklahoma: 

Gould  and  Taylor.    Okla.  Geol.  Surv.,  Bull.  5,  1911. 
Oregon: 

Darton.     U.  S.  Geol.  Surv.,  Bull.  387,  1909.     (Limestones.) 
Pennsylvania: 

Hopkins.     Penn.    State    College,    Ann.    Rept.,    1895;    Appendix,    1897;  also 

U.  S.  Geol.  Surv.,  i8th  Ann.  Rept.,  V,  p.  1025,  1897.     (Brownstones.) 
Rhode  Island: 

Dale.    U.  S.  Geol.  Surv.,  Bull.  354,  1908.     (Granites.) 
South  Carolina: 

Watson.     U.  S.  Geol.  Surv.,  Bull.  426,  1910.     (Granites.) 

Sloan.     S.  C.  Geol.  Surv.,  Series  IV,  Bull.  2 .  p.  162,  1908. 
South  Dakota: 

Todd.     S.  Dak.  Geol.  Surv.,  Bull.  3,  p.  81,  1902. 


go  BUILDING  STONES  AND   CLAY-PRODUCTS 

Tennessee: 

Keith.    U.  S.  Geol.  Surv.,  Bull.  213,  p.  366,  1903.     (Marbles.)     See  also 

Merrill's  book,  mentioned  above. 
Texas: 

Burchard.     U.  S.  Geol.  Surv.,  Bull.  430  F. 
Vermont: 

Perkins.  Report  of  State  Geologist  on  Mineral  Industries  of  Vermont, 
1899-1900,  1903-1904,  1907-1908;  also  Report  on  Marble,  Slate  and 
Granite  Industries,  1898. 

Dale.     U.  S.  Geol.  Surv.,  Bull.  404,  1909.     (Granite.) 

Ries.     i8th  Ann.  Rept.  U.  S.  Geol.  Surv.     (Marble.) 
Virginia: 

Watson.     Min.  Res.  of  Va.,  Lynchburg,  1907. 

Watson.     U.  S.  Geol.  Surv.,  Bull.  426,  1910.     (Granites.) 
Washington: 

Shedd.    Wash.  Geol.  Surv.,  II,  p.  3,  1902. 
West  Virginia: 

Grimsley.    W.  Va.  Geol.  Surv.,  Ill,  1905.     (Limestones.) 

Ibid,  IV,  p.  355,  1909.     (Sandstones.) 

Dale.     U.  S.  Geol.  Surv.,  Bull.  275,  1906.     (Slate.) 
Wisconsin: 

Buckley.     Wis.  Geol.  and  Nat.  Hist.  Surv.,  Bull.  IV,  1898. 
Wyoming: 

Knight.     Eng.  and  Min.  Jour.,  LXVI,  p.  546,  1898. 


PLATE  XIX.  —  Church  in  Mexico  City  constructed  of  volcanic  tuff. 


CHAPTER  III. 
IGNEOUS  ROCKS  (CHIEFLY  GRANITES)  AND  GNEISSES. 

OF  the  many  kinds  of  igneous  rocks,  the  granites  and  granite- 
gneisses  are  more  extensively  employed  for  building  stones  than 
any  others  in  the  United  States. 

This  is  due  to  several  causes,  such  as  wider  distribution,  more 
pleasing  color  and  greater  regularity  of  structure  and  jointing. 
Syenites  are  rare  and  so  are  the  diorites,  and  hence  they  are 
little  quarried.  Gabbros  are  not  only  too  dark  in  color  to  suit 
most  architects,  but  it  is  difficult  to  supply  large-dimension 
stones  of  them.  They,  or  certain  closely  related  rocks,  have, 
however,  sometimes  been  used  for  monumental  work.  Diabase 
and  basalt  are  abundant  in  some  regions,  the  former  for  example 
in  New  Jersey,  New  York  and  Connecticut;  the  latter  in  Wash- 
ington and  Idaho;  both  are  utilized  mainly  for  paving  blocks 
and  road  material. 

The  volcanic  rocks,  such  as  rhyolite  and  trachyte,  as  well  as 
the  consolidated  volcanic  tuffs,  are  abundant  in  the  far  west, 
and  are  of  importance  in  some  districts.  They  are,  however, 
apt  to  be  very  porous,  and  some  are  sufficiently  soft  to  be  cut 
with  a  saw.  For  this  reason,  selection  should  be  made  with 
care,  the  softer  and  more  porous  ones  being  used  only  in  mild 
and  dry  climates.  To  the  southward  in  Mexico  these  soft  vol- 
canic materials  find  great  favor  for  both  constructional  work 
and  ornamental  purposes.  Plate  XIX  shows  a  church  in  Mexico 
City  built  of  this  class  of  stone  and  brings  out  well  its  possi- 
bilities. 

Since  the  granites  are  the  most  widely  used  of  the  igneous 
rocks,  their  properties  have  been  more  thoroughly  investigated 
in  this  country,  and  it  is  chiefly  these  which  are  referred  to  in 
the  pages  immediately  following.  It  may  be  said,  however, 
that  the  gneisses  and  many  of  the  other  igneous  rocks  of  granitic 

93 


94  BUILDING  STONES  AND   CLAY-PRODUCTS 

texture  are  similar  to  granites  in  their  absorption,   crushing 
strength,  transverse  strength,  fire  resistance,  etc. 

Characteristics  of  Granites.1  As  commonly  used  by  quarry- 
men,  the  term  granite  includes  all  igneous  rocks  and  gneiss. 
It  seems  best,  however,  to  use  it  in  the  geological  sense,  which  is 
more  restricted.  It  may,  therefore,  be  defined  as  an  evenly 
crystalline,  plutonic,  igneous  rock,  consisting  of  quartz,  ortho- 
clase  feldspar  and  mica,  hornblende  or  pyroxene. 

There  are  also  varying  but  usually  small  quantities  of  other 
feldspars,  and  there  are  a  large  number  of  subordinate  accessory 
minerals,  few  of  which,  except  the  pyrite  and  garnet,  are  likely 
to  be  recognized  by  anyone  not  having  a  knowledge  of  mineralogy. 
Granites  may  be  even-grained  or  porphyritic  in  their  texture. 
The  former  may  be  subdivided  into  coarse,  medium  and  fine, 
in  which  the  feldspars  measure  two-fifths  and  one-fifth,  and  under 
one-fifth  inch  respectively. 

The  average  specific  gravity  of  granite  is  about  2.662,  which 
is  equivalent  to  two  long  tons,  or  4480  pounds  per  cubic  yard, 
and  about  165  pounds  to  the  cubic  foot. 

The  ultimate  crushing  strength  of  granite  was  found  by  Buck- 
ley in  Wisconsin  ones2  to  vary  from  about  15,000  to  43,973  pounds 
per  square  inch,  but  15,000  to  30,000  would  be  the  more  usual 
range. 

Elasticity.  This  property  is  rarely  tested.  But  specimens 
from  Arkansas,  Connecticut,  Maine,  Minnesota  and  New  Hamp- 
shire, showed  that  pieces  with  a  gaged  length  of  20  inches,  and 
a  diameter  of  5.5  inches  at  the  middle,  when  placed  under  a  load 
of  5000  pounds  per  square  inch,  compressed  from  0.0108  to 
0.0245  inch.  This  resulted  in  a  lateral  expansion  of  from 
0.005  to  0.007  inch,  and  gave  ratios  of  lateral  expansion  to 
longitudinal  compression  ranging  from  i  :  8  to  i  :  47  (Test  of 
Metals  (1895),  1896,  pp.  339-348). 

Flexibility.  Granite,  in  spite  of  its  apparently  rigid  character, 
is  flexible  in  sheets  of  sufficient  thinness  and  area.  Dale  states 

1  For  an  excellent  discussion  of  the  properties  of  granites  see  Dale,  U.  S.  Geol. 
Surv.,  Bull.  313. 

2  Bull.  Wis.  Geol.  and  Nat.  Hist.  Surv.,  4,  p.  361,  390. 


IGNEOUS  ROCKS   (CHIEFLY  GRANITES)   AND  GNEISSES      95 


that  sheets  J  inch  thick  and  4  feet  long,  from  a  Maine  quarry, 
were  flexible,  but  suggests  that  this  flexibility  may  have  been 
due  to  the  partially  disintegrated  character  of  the  stone.1 

Expansibility.     This  is  referred  to  under  permanent  swelling. 

Porosity.  The  porosity  of  granites  is  usually  small.  Buckley 
gave  that  of  14  Wisconsin  granites  as  ranging  from  0.17  to  0.392 
per  cent,  while  in  Maryland  granites,  according  to  Merrill,  it  is 
from  0.196  to  0.258.  Granite  also  absorbs  a  slight  amount  of 
water,  usually  under  i  per  cent  if  the  stone  is  fresh. 

Fire  Resistance.  Granite  spalls  off  badly  under  the  combined 
influence  of  fire  and  water,  which  may  be  due  to  the  differential 
expansion  and  contraction  of  the  outer  and  inner  portions  of  a 
block.  It  may  also  be  connected  with  the  vitreousness  of  the 
quartz  and  the  presence  of  liquids  contained  in  microscopic 
cavities  of  the  quartz. 

Chemical  Composition.  The  two  following  analyses  represent, 
I,  the  average  chemical  composition  of  granite  as  given  by 
Merrill  and,  II,  the  average  composition  of  21  Georgia  granites 
given  by  Watson: 


I. 

II. 

Silica                           .    .    . 

72  .00 

69.97 

Alumina  
Iron  oxide  
Magnesia  
Lime 

iS-°7 

2.22 
0.50 
2    OO 

16.63 
1.28 

o-55 
2.13 

Potash 

412 

4-  71 

Soda   . 

2    OO 

4-73 

Loss  on  ignition 

I    IO 

Classification.  For  scientific  purposes  granites  might  be  classi- 
fied according  to  the  less  essential  mineral  constituents,  as  mica, 
hornblende  and  augite,  or  a  more  complex  scheme  classifies 
them  according  to  their  mineral  and  chemical  composition. 

For  economic  purposes,  granites  may  be  classified  according 
to  their  texture,  as  even-grained  or  porphyritic,  or  as  coarse, 
medium  and  fine.  Again  color  and  shade  may  be  used  as  the 
basis  for  grouping.  Some  may  prefer  a  grouping  according  to 
uses.  None  of  these  are  wholly  satisfactory. 

1  U.  S.  Geol.  Surv.,  Bull.  313,  pp.  22  and  151,  1907. 


96  BUILDING  STONES  AND   CLAY-PRODUCTS 

Structure  of  Granites-  Some  granites  may  indicate  the  direc- 
tion in  which  the  molten  rock  flowed  before  cooling,  by  streaks 
or  sheets  of  mica  scales  parallel  to  the  direction  of  the  line  of 
contact  between  two  granites.  The  character  is  a  purely  local 
one,  and  is  not  to  fre  confused  with  gneissic  structure  (Dale). 

The  rift  is  an  obscure  foliation,  either  vertical  (or  nearly  so)  or 
horizontal,  along  which  the  granite  splits  more  readily  than  in  any 
other  direction,  while  the  grain  is  a  direction  at  right  angles  to 
the  rift,  along  which  the  stone  also  splits,  but  less  readily. 

Microscopic  examination  of  the  stone  shows  that  the  rift  may 
be  due  to  microscopic  faults  which  may  cut  through  both  the 
quartz  and  feldspar  grains. 

Rift  and  grain  are  not  necessarily  pronounced ;  indeed,  either 
or  both  may  be  feeble  or  absent.  The  rift  may  sometimes  change 
its  course,  and  this  the  quarryman  terms  the  run. 

Cut-off  or  hardway  is  the  quarrymen's  term  for  the  direction 
along  which  the  granite  must  be  channeled  because  it  will  not  split. 

Sheets  or  beds  are  terms  used  to  designate  the  division  of  granite 
by  joint-like  fractures  which  are  variously  curved  or  nearly 
horizontal,  and  generally  parallel  with  the  surface.  They  some- 
times become  thicker. 

Joints  are  found  in  almost  every  granite  quarry.  In  some  they 
are  regular,  but  in  others  exceedingly  irregular,  so  that  the  granite 
is  broken  up  into  a  number  of  polygonal  blocks.  Where  the 
granites  have  been  weathered  along  such  joints  the  blocks  re- 
semble boulders,  hence  the  name  boulder  quarries.  Such  quarries 
are  more  common  in  the  sou  them  states  than  in  the  northern  ones. 

Dale  states  that  in  some  quarries  the  "  granite  near  the  sur- 
face acquires  a  marked  foliation,  which  appears  to  be  parallel  to 
the  sheet  structure,  and  possibly  to  the  rift.  This  foliation  is 
known  by  quarrymen  as  shakes.  It  occurs  both  at  the  top  and 
.at  the  bottom  of  the  sheet,  through  a  maximum  thickness  of  six 
inches.  It  is  coextensive  with  the  discoloration  known  as  sap 
and  occurs  at  many  places  near  vertical  joints." 

Knots  are  segregations  of  the  darker  minerals  forming  dark, 
unsightly  spots  in  granite,  and  may  cause  the  rejection  of  those 
portions  of  the  stone  in  which  they  occur. 


PLATE  XX,  Fig.  i.  —  Granite  quarry,  Hardwick,  Vt. 


PLATE  XX,  Fig.  2.  —  Granite  quarry  at  North  Jay,  Me.     (Photo  loaned  by 
Maine  and  New  Hampshire  Granite  Company.) 

97 


IGNEOUS  ROCKS  (CHIEFLY  GRANITES)  AND  GNEISSES        99 

Inclusions.  Many  granites  contain  angular  or  irregular  frag- 
ments of  other  rocks,  such  as  schists,  gneisses  or  even  other 
granites,  which  became  incorporated  in  the  granite  itself  during 
its  intrusion.  Those  portions  of  the  rock  containing  them  are 
usually  discarded. 

Dikes.  In  some  granite  quarries  the  stone  is  traversed  by 
dikes  of  other  igneous  rock,  such  as  diabase,  or  in  some  cases 
pegmatites,  the  latter  being  regardable  as  a  very  coarse-grained 
granite.  These  dikes  may  be  both  large  and  small,  and  blocks 
containing  them  are  of  no  value  for  structural  purposes. 

Black  Granites.  This  term,  suggested  by  Dale,  is  a  good 
one  to  use  for  commercial  purposes  and  may  include  a  variety 
of  igneous  rocks  of  prevailingly  dark  color,  such  as  gabbros, 
diorites,  diabases,  etc.  Their  characters  have  been  previously 
referred  to. 

The  black  granites  correspond  to  the  fine  and  medium-grained 
granites  in  their  texture,  but,  aside  from  their  greater  toughness, 
they  probably  vary  but  little  in  their  physical  properties  from 
granites  of  the  same  grade  and  texture.  We  are  not  so  familiar 
with  their  physical  properties,  for  the  reason  that  their  use  for 
structural  purposes  is  limited,  and  they  have  not  been  studied  in 
detail.  The  weight  per  cubic  foot  of  the  black  granites  is  greater 
than  that  of  the  common  granites,  the  gabbros  ranging  in  specific 
gravity  from  2.66  to  about  3  and  the  diabases  from  2.7  to  2.98, 
while  the  diorites  average  about  2.95.  Their  chief  use  is  for 
monumental  work. 

Tests  of  Granite.  These  may  include  the  ordinary  tests  made 
on  all  building  stones  such  as  the  determination  of  the  crushing 
strength,  transverse  strength,  absorption,  porosity,  specific 
gravity,  fire  test,  freezing  test,  coefficient  of  expansion,  presence 
of  calcium  carbonate  and  ability  to  take  a  polish.  These  have 
been  discussed  in  the  preceding  chapter. 

A  number  of  tests  of  granite  have  been  published,  but  un- 
fortunately most  of  them  are  only  determinations  of  the  crushing 
strength  and  absorption.  It  is,  therefore,  difficult  to  present  a 
large  series  of  complete  tests.  The  following,  however,  will  serve 
to  give  some  idea  of  the  variation  shown  by  different  granites: 


100 


BUILDING  STONES  AND   CLAY-PRODUCTS 


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PLATE  XXI.  —  Map  showing  distribution  of  igneous  rocks  and  gneisses  in  1 


95° 


300  *§0  500  600 

United  States.     (After  G.  P.  Merrill,  "Stones  for  Building  and  Decoration.") 


103 


IGNEOUS  ROCKS  (CHIEFLY  GRANITES)  AND  GNEISSES       105 

Uses  of  Granite.  Granites,  on  account  of  their  usually  great 
durability,  variety  of  color,  and  texture  are  among  our  most 
widely  used  building  stones.  The  coarser  and  medium-grained 
ones  are  best  adapted  to  massive  masonry  work,  while  the  finer 
and  even-textured  ones  are  most  sought  after  for  monumental 
work  and  structural  work  of  finer  lines.  The  darker  granites 
often  give  excellent  contrast  between  polished  and  hammered 
surfaces. 

Certain  ones,  however,  like  the  Quincy,  Mass. ;  North  Jay,  Me. ; 
Westerly,  R.  I.;  Barre,  Vt.,  and  others,  have  been  especially 
much  used  for  monuments. 

At  almost  every  granite  quarry  there  is  more  or  less  small-sized 
stone,  which  is  used  for  paving  blocks,  and  crushed  stone. 

DISTRIBUTION   OF  IGNEOUS  ROCKS    (CHIEFLY  GRANITES)   AND 
GNEISSES  IN  THE  UNITED   STATES. 

Granite  forms  an  important  source  of  building  stone,  some- 
what widely  distributed  in  the  United  States,  but  probably 
70  per  cent  of  that  quarried  comes  from  the  eastern  United 
States,  where  the  extensive  deposits,  owing  to  their  favorable 
location  for  working  and  shipment,  together  with  their  nearness 
to  large  markets,  have  been  developed  on  an  enormous  scale.  The 
other  kinds  of  igneous  rock  are  used  to  a  much  more  limited  extent 
than  the  granite.  Gneisses,  usually  of  granitic  composition,  are 
also  widely  employed  in  the  eastern  states. 

The  areas  which  may  be  considered  are:  (i)  Eastern  Belt 
extending  from  Maine,  south  westward  to  eastern  Alabama.  (2) 
Minnesota- Wisconsin  Area.  (3)  Southwestern  Area  including 
isolated  districts  in  Missouri,  Arkansas,  Oklahoma  and  Texas. 
(4)  Cordilleran  Area  including  parts  of  Colorado,  California  and 
other  western  states.  (5)  Black  Hills  Area  of  South  Dakota, 
with  a  great  mass  of  undeveloped  granite. 

EASTERN  BELT. 

In  this  belt,  whose  limits  were  referred  to  above,  granite  quar- 
ries have  been  opened  up  in  Maine,  New  Hampshire,  Vermont, 
Massachusetts,  Rhode  Island,  Connecticut,  New  York,  New 
Jersey,  Pennsylvania,  Maryland,  Virginia  and  Georgia.  Those 


106  BUILDING   STONES  AND   CLAY-PRODUCTS 

of  the  New  England  area  are  specially  prominent.  While  they 
are  nearly  all  true  granites  mineralogically,  those  in  the  southern 
half  of  the  belt  especially  often  show  a  gneissic  structure.  No 
attempt  will  be  made  here  to  describe  all  the  quarries,  but  simply 
to  mention  the  more  important  localities  in  each  state,  with  a 
brief  statement  of  the  character  of  the  stone. 

References  are  given  in  the  bibliography  at  the  end  of  Chap- 
ter II. 

MAINE. 

With  the  exception  of  the  important  quarries  of  Hallowell  in 
Kennebec  County,  North  Jay  in  Franklin,  and  a  few  minor  ones, 
all  the  Maine  granite  quarries  are  located  along  the  seaboard, 
but  the  industry  has  its  center  in  Penobscot  and  Blue  Hill  bays 
and  the  islands  around  them. 

There  are  said  to  be  about  12  quarries  in  black  granite,  located 
in  York,  Lincoln,  Penobscot  and  Washington  counties,  and  the 
product  of  these  is  used  in  comparatively  small  amounts  for 
expensive  work. 

The  characteristics  of  the  Maine  granites  may  be  summarized 
as  follows: 

North  Jay.  A  biotite-muscovite  granite,  known  as  "  White 
granite, "  of  fine,  even-grained  texture.  It  does  not  take  a  very 
good  polish,  owing  to  the  abundance  of  mica  scales.  The  product 
is  used  for  monuments  and  buildings,  the  chief  market  being  in 
the  west. 

Examples.  —  General  Grant's  tomb,  Riverside  Drive,  New  York  City;  Hahne- 
mann  monument,  Washington,  D.  C.;  Chicago  and  Northwestern  Railroad 
Building,  Chicago;  Western  German  Bank,  Cincinnati,  Ohio;  Marshall  Field  store, 
Chicago.  The  refuse  is  used  for  rough  stone,  paving  blocks  and  crushed  stone. 

Crotch  Island.  A  biotite  granite,  of  lavender,  medium  gray 
color,  and  coarse  but  even-grained  texture,  whose  chief  use  is 
in  massive  construction  work,  especially  in  New  York  City. 

Examples.  —  Blackwells  Island  Bridge  and  Ninth  Regiment  Armory,  New 
York  City;  Post  Office,  Lowell,  Mass.;  Steps  of  Library,  Columbia  University, 
New  York  City. 

Hallowell.  Biotite-muscovite  granite,  light  gray  shade  and 
fine  texture,  with  porphyritic  feldspars  of  about  one-quarter  inch 
diameter.  It  takes  a  fine  polish,  and  the  face  so  treated  has  a 


11 

80 


I 

22 


107 


IGNEOUS  ROCKS  (CHIEFLY  GRANITES)  AND  GNEISSES       109 

bluish  tinge.     It  is  used  for  buildings  and  sculpture,  and  is  well 
adapted  to  statuary  and  delicate  ornamental  work. 

Examples.  —  Albany  Capital,  Albany,  N.  Y.;  Hall  of  Records  (including 
statuary),  New  York  City;  Masonic  Temple,  Boston,  Mass.;  Illinois  Trust  Com- 
pany, Chicago,  111.;  Northwestern  Insurance  Company  building,  Milwaukee; 
Statuary  on  Plymouth  monument,  Mass.;  Soldiers'  monument,  Gettysburg; 
Suffolk  Savings  Bank,  Boston.  The  waste  is  used  for  paving  blocks. 

Vinalhaven  and  Hurricane  Islands.  These  and  the  adjacent 
islands  are  known  collectively  as  the  Fox  Islands,  and  their 
granite  as  the  Fox  Island  granite.  The  rock  is  mostly  a  bio- 
tite-granite,  pinkish  buff,  medium  gray  in  color,  and  of  coarse, 
even-grained  texture.  It  takes  a  good  polish  but  the  size  of  the 
mica  plates  is  not  favorable  to  its  being  durable  on  continued 
exposure.  The  stone  is  used  for  docks,  bridges,  piers,  buildings 
and  monuments. 

Examples.  —  New  Post  Office,  Washington,  D.  C.;  Masonic  Temple,  Philadel- 
phia; General  Wool  monument,  Troy;  Manhattan  Bank,  New  York  City. 

The  Palmer  or  Wharf  quarry  of  this  region  supplied  8  columns,  51^  to  54  feet 
by  6  feet,  for  the  Cathedral  of  St.  John  the  Divine  in  New  York  City.  These  were 
to  have  been  cut  in  one  piece,  with  the  longer  axes  at  right  angles  to  the  rift.  In 
the  lathe,  however,  the  strain  came  upon  the  weakest  part  of  the  stone,  and  as  it 
had  been  subjected  to  torsional  strain  by  the  application  of  rotary  power  from  one 
end  only,  it  broke  diagonally.  The  columns  therefore,  had  to  be  made  26  foot 
lengths. 

Red  Beach.  A  biotite-granite  of  bright  pink  color  and  medium, 
even-grained  texture.  It  takes  a  high  polish  of  good  durability, 
and  is  the  brightest  red  granite  occurring  in  Maine,  being  shipped 
all  over  the  United  States  for  monumental  work. 

Examples.  —  Part  of  American  Museum  of  Natural  History,  New  York  City; 
Pedestal  of  General  Grant  Monument,  Galena,  111. 

Addison.  The  stone  quarried  here  is  an  hypersthene-olivine 
gabbro  of  nearly  black  color,  and  the  polished  surface  is  jet 
black  mottled  with  a  little  white.  In  some  quarries  a  somewhat 
lighter  colored  variety  is  obtained. 

The  stone  shows  excellent  contrast  —  the  almost  white  ham- 
mered surface  comparing  well  with  the  dark  polished  face.  It 
is  used  for  monuments  and  interior  decoration. 

Examples.  —  Base  of  wainscoting,  Philadelphia  City  Hall;  Danforth  Monu- 
ment, Morristown,  N.  J.;  Zeller  Monument,  Lewisburg,  Pa.;  center  monument 
at  Greenwood  Cemetery,  Brooklyn,  N.  Y. 


110  BUILDING   STONES  AND   CLAY-PRODUCTS 

Jonesboro.  A  biotite  granite  of  grayish-pink  color  and  slightly 
coarse,  even-grained  texture.  The  stone  takes  a  good  polish 
of  durable  nature. 

Examples.  —  Custom  House  and  Post  O.TEice,  Buffalo,  N.  Y.;  Custom  House  and 
Post  Office,  Fall  River,  Mass.;  Western  Savings  Bank  Building,  Philadelphia; 
Pullman  Office  Building,  Chicago,  111.;  Wellington  Building  and  Jordan  Marsh 
&  Company  Building,  Boston,  Mass.;  Fidelity  and  Trust  Building,  Newark,  N.  J. 

The  following  additional  examples  of  other  granites  may 
simply  be  mentioned. 

Blue  Hill.  Mess  Hall,  Soldiers  Home,  Washington,  B.C.; 
Manhattan  Trust  Building,  New  York  City;  Post  Office,  Harris- 
burg,  Pa. 

Brookville.  Bronx  Court  House,  New  York  City;  Post  Office, 
Middletown,  N.  Y. 

Dix  Island.  New  York  Post  Office;  Philadelphia  Post  Office; 
Treasury  Building,  Washington. 

Clark's  Island.  Post  Office,  Hartford,  Conn. ;  Atlantic  Trust 
Co.,  New  York  City. 

Machias.  Elliot  Hall,  Cambridge;  Chapel,  Mt.  Hope  Ceme- 
tery, Bangor,  Me. 

Pleasant  River.     Wainscoting,  Philadelphia  City  Hall. 

Stonington.  Several  bridges  across  Harlem  River,  New  York 
City. 

Classification  of  Maine  Granites.  Dale  gives  the  following 
economic  classification  of  Maine  granites. 

1.  Reddish  (medium  to  coarse) . 

Light:   Wells,  Black  Island,  Mount  Desert. 

Swans'  Island  (Toothachers'  Cove). 
Bright:    Redbeach. 
Dark:     Shattuck   Mountain,   Redbeach,   Jonesport    (Head   Harbor  and 

Hardwood  Islands),  Marshfield,  Black  Island,  Mount  Desert,  Jonesboro. 

2.  Pinkish  buff  (medium  to  coarse). 

Vinalhaven  (in  part),  Hurricane  Island,  High  Island,  Dix  Island,  Swans 
Island,  Biddeford,  Stonington  (Deer  Isle,  Crotch  Island,  Green  Island). 

3.  Light  lavender  (medium  to  coarse). 

Stonington,  Crotch  Island,  Deer  Isle,  Moose  Island,  Jonesboro. 

4.  Gray  (medium  to  coarse);    black  and  white,  latter  dominant,  strong  con- 

trasts.    Feldspar  in  some  rocks,  slightly  bluish. 

Biddeford,    Kennebunkport,    Blue    Hill,    South    Thomaston,    Guilford 
Norridgewock,  South  Brookville. 


IGNEOUS  ROCKS  (CHIEFLY  GRANITES)  AND  GNEISSES        III 

5.  Gray,    with    isolated    lighter    crystals.     Frankfort,    Searsport,    Blue    Hill, 

Dedham. 

6.  Buff  (medium  to  coarse). 

Millbridge,  Mount  Desert,  Brooksville,  Sedgwick. 

7.  Greenish  gray  (medium  coarse). 

Mount  Desert,  Alfred. 

8.  Black  and  white  (medium  texture,  black  dominant). 

Spruce  Head,  Hartland,  Woodstock,  Norridgewock. 

9.  Gray,  weak  contrasts  (medium  to  coarse  texture). 

Sullivan,  Franklin. 

10.  Muscovite,  white  mica  conspicuous  (medium  texture). 

Fryeburg,  Oxford,  Bradbury. 

11.  Fine  textured  (light  to  medium  gray). 

Jay,  Pownal,  Swanville,  Lincoln,  Hallowell,  Freeport,  Frankfort,  Blue 
Hill,  Clark  Island,  Long  Cove,  Brunswick,  Crotch  Island,  Waldoboro, 
Norridgewock. 

12.  Very  coarse  (gray  or  pinkish  buff). 

Stonington,  Dedham,  Franklin. 

13.  Paving  (fine,  with  isolated  crystals). 

Vinalhaven,  Mount  Desert. 

14.  Black  (fine  to  coarse).     Black  and  black  speckled. 

Vinalhaven,  Addison,  Calais. 
Greenish  black. 

Belfast,  South  Berwick,  Hermon. 
Dark  gray. 

Sullivan,  Barleyville,  Redbeach,  Calais,  St.  George,  Round  Pond  quarry. 
Medium  gray. 

Round  Pond  quarry,  Whitefield. 

NEW  HAMPSHIRE. 

The  commercial  granites  of  New  Hampshire  afford  a  variety 
of  rocks,  as  can  be  seen  in  the  summarized  table.  The  most 
important  constructional  ones  are  those  of  Concord,  Fitzwilliam, 
Marlboro,  Lebanon,  Canaan  and  Redstone,  while  the  monu- 
mental granites  include  those  of  Fitzwilliam,  Troy,  Milford  and 
Brookline. 

The  most  notable  structure  of  New  Hampshire  granite 
erected,  according  to  Dale,  is  the  library  of  Congress. 

Some  of  the  more  important  granites  are  referred  to  in  detail 
below,  while  all  are  mentioned  in  a  summarized  table  prepared 
by  T.  N.  Dale,  given  on  a  later  page. 

Concord.  A  muscovite-biotite  granite,  of  medium  and  bluish 
gray  color,  and  a  texture  from  fine  to  medium  though  somewhat 
porphyritic.  It  takes  a  fair  polish,  but  has  rather  too  much 


112  BUILDING   STONES  AND   CLAY-PRODUCTS 

mica.     Considerable  contrast  is  obtained  between   the   rough 
and  hammered  surface. 

Examples.  —  Blackstone  Library,  Chicago;  Christian  Science  Church,  New 
York  City;  German- American  Savings  Bank,  Pittsburg,  Pa.;  outer  walls,  Con- 
gressional Library,  Washington;  City  Hall  and  Christian  Science  Church,  Boston; 
Post  offices  at  Lincoln,  Neb.;  Adrian,  Mich.;  and  Hammond,  Ind. 

Milford.  Quartz  monzonite,  of  light,  medium  and  dark  gray 
shades,  in  places  of  a  slight  bluish,  pinkish  or  buff  tinge,  and 
always  spangled  with  black  mica.  Texture,  even-grained,  very 
fine  to  fine.  The  finer  ones  are  properly  monumental  granites, 
take  a  high  polish  and  give  good  contrast.  The  finer  ones 
show  a  uniformity  and  delicacy  of  shade  and  tint.  The  coarser 
ones  are  for  constructional  work. 

Examples.  —  Majestic  Theatre,  Chicago,  111. ;  east  front  Treasury  Building, 
Washington,  D.  C.;  Post  Office,  Lawrence,  Mass. 

Conway.  The  granites  are  all  coarse,  constructional  ones, 
mostly  pinkish,  mottled  with  gray  and  spotted  with  black. 
They  are  biotite  or  biotite-hornblende  granites.  Some  are 
greenish. 

The  Redstone  quarry  rock  takes  a  high  polish,  but  the  large 
size  of  the  mica  scales  is  not  favorable  to  the  durability  of  same 
under  long-continued  exposure.  This  is  mainly  a  constructional 
granite. 

Examples.  —  First  National  Bank,  Chicago;  Franklin  Savings  Bank,  New 
York  City;  Union  Station,  Pittsburg;  First  and  Fourth  National  Banks,  Cincin- 
nati, with  polished  columns;  High  School,  Springfield,  Mass.;  the  Redstone  green, 
Fidelity  Mutual  Life  Insurance  Building,  Philadelphia;  polished  columns  on 
Northwestern  Guarantee  Loan  Company's  Building,  Minneapolis. 

Auburn.  This  granite  belongs  to  the  same  general  granite 
area  as  the  Concord.  The  granite,  "  deep  pink  Auburn,"  is  a 
quartz  monzonite  of  medium  pink  buff  color  with  fine,  black 
dots.  The  texture  is  fine.  The  stone  takes  a  fair  polish,  and 
the  hammered  face  by  its  lightness  makes  good  contrast  with 
rough  and  polished  surfaces. 

Troy.     This  is  similar  to  the  North  Jay,  Me.,  which  see. 

Fitzwilliam.  Muscovite-biotite  granite,  light,  bluish  gray 
color,  and  even,  fine-grained  texture.  Used  mainly  for  buildings 
and  monuments. 


IGNEOUS  ROCKS  (CHIEFLY  GRANITES)  AND  GNEISSES       113 
Some  takes  a  good  polish. 

Examples.  —  City  Hall,  Newark,  N.  J.;  approaches  and  bases  of  First  Church 
of  Christ,  Scientist,  Boston;  Smith  Mausoleum,  Paducah,  Ky.;  Tanner  Mauso- 
leum, Springfield,  111. 

The  "  snow-flake"  granite  from  here  is  a  biotite-muscovite 
granite,  of  light  to  medium  gray  shade,  and  porphyritic  texture. 
It  is  used  for  buildings  and  monuments. 

Examples.  —  Art  Museum,  Toledo,  Ohio;  Law  Building,  Iowa  University; 
Post  offices  at  Muskegon,  Mich.;  Grand  Island,  Neb.;  Bedford,  Ind.;  Devil's 
Lake,  N.  Dak.;  Ithaca,  N.  Y. 

Other  grades  from  here  are  the  "  Marlboro, "  the  "  Troy 
white."  Latter  widely  used,  and  lends  itself  well  to  carving. 

Examples.  —  Bank  of  Pittsburg,  Pittsburg,  Pa.;  Metropolitan  Savings  Bank, 
Baltimore,  Md.;  Steps  and  approaches  to  Library  of  Congress,  Washington,  and 
New  York  Library;  Mark  Hanna  mausoleum,  Cleveland,  Ohio. 

Mascoma  Granite,  near  Enfield.  A  biotite  gneiss  of  light  buff- 
gray  color  speckled  with  black,  and  of  even-grained,  somewhat 
gneissoid,  coarse  texture.  It  is  a  constructional  stone,  somewhat 
resembling  that  from  Milford,  Mass.,  takes  fair  polish  and  face 
shows  some  magnetite. 

Examples.  —  Plain  Dealer  Building,  Cleveland,  Ohio;  Carnegie  Institute,  Pitts- 
burg, Pa.;  Royal  Bank  of  Canada,  Winnipeg,  Man.;  Agricultural  National  Bank, 
Pittsfield,  Mass.;  Jamestown  Monument,  Jamestown  Id.,  Va. 

Classification  of  New  Hampshire  Granites.  The  following 
classification  of  the  commercial  granites  of  New  Hampshire  is 
given  by  Dale. 


114 


BUILDING  STONES  AND  CLAY-PRODUCTS 


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IGNEOUS  ROCKS  (CHIEFLY  GRANITES)  AND  GNEISSES       115 


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Il6  BUILDING   STONES  AND   CLAY-PRODUCTS 

VERMONT. 

The  commercial  granites  of  Vermont  are  of  three  kinds: 
Biotite  granite,  quartz  monzonite  and  hornblende-augite  granite. 
To  the  first  class  belong  those  of  Woodbury,  Newark  and  most 
of  Barre,  to  the  second  those  of  Bethel,  Randolph,  Rochester, 
Calais,  Derby,  Dummerston,  Hardwick  (Buffalo  Hill),  Kirby, 
Groton,  Topsham,  and  some  in  Cabot.  To  the  third,  those  of 
Mount  Ascutney  in  Windsor.  The  Ryegate  ones  belong  to  both 
the  first  and  second. 

A  few  may  be  mentioned  briefly: 

Hardwick.  The  granite  from  the  Buffalo  Hill  quarry,  known  as 
the  "  Dark  Blue  Hardwick"  is  a  quartz  monzonite  of  dark  gray 
shade,  a  little  darker  than  "  Dark  Barre"  and  a  little  lighter  than 
11  Dark  Quincy."  The  -texture  is  medium.  It  is  a  bright  granite 
with  strong  contrast  between  the  white  feldspar  and  black  mica 
and  takes  a  fair  polish.  It  hammers  light,  offering  a  marked 
contrast  to  the  polished  surface.  The  latter  shows  some  pyrite 
and  magnetite. 

Bethel.  This  is  known  commercially  as  the  "  Bethel  White 
Granite"  and  the  "Hardwick  White  Granite."  It  is  a  quartz 
monzonite  of  very  light  color,  medium  texture,  and  relatively 
hard.  It  takes  a  high  polish. 

Examples.  —  Wisconsin  State  Capitol,  Madison,  Wis. ;  Title  Guarantee  and 
Trust  Co.'s  Building,  New  York  City;  Old  Colony  Trust  Company's  Building, 
Boston,  Mass.;  Union  Station,  Plaza,  Washington,  D.  C. 

Barre.  To  the  southeast  and  northeast  of  the  city  of  Barre 
there  are  about  sixty  quarries  producing  the  lt  Barre"  granite. 
The  stone  is  a  biotite  granite  which  owes  its  different  shading 
partly  to  the  varying  content  of  biotite,  and  partly  to  different 
degrees  of  alteration  of  the  feldspar. 

Dale  names  the  following  shades :  (i)  Very  light  gray  (Wheaton 
quarry),  equivalent  to  that  of  North  Jay,  Me.;  (2)  Light,  in- 
clining to  medium,  slightly  bluish  gray  (Jones  light  quarry), 
between  that  of  North  Jay  and  of  Hallowell,  Me.;  (3)  Light, 
medium  bluish  gray  (Smith  upper  quarry),  between  that  of 
Hallowell,  Me.,  and  Concord,  N.  H.;  (4)  Medium  bluish  gray 
(Duffee  quarry),  a  trifle  darker  than  "  Concord  granite;"  (5) 


10  O 10 ZO  30  40  MILES 


PLATE  XXm.  —  Map  of  Vermont  showing  granite  centres  and  prospects. 
(After  Dale,  U.  S.  Geol.  Surv.,  Bull.  404.) 


117 


IGNEOUS  ROCKS  (CHIEFLY  GRANITES)  AND  GNEISSES        119 

Dark,  inclining  to  medium  bluish  gray  (Bruce  quarry) ;  (6)  Dark 
bluish  gray  (Marr  &  Gordon  quarry) ;  (7)  Very  dark  bluish  gray 
(Marr  &  Gordon  quarry  knots),  equivalent  to  "  Dark  Quincy." 
The  chief  production  is  of  3,  4  and  5. 

Barre  granite  is  used  mainly  for  monumental  purposes,  a  small 
quantity  only  being  employed  for  constructional  work.  The 
light,  medium  and  dark  monumental  granites  do  not  afford 
strong  mineral  contrasts  in  the  rough,  but  polishing  improves 
this.  The  "  light  Barre"  is  never  polished,  but  hammered,  be- 
cause of  the  poor  contrast  between  polished  and  hammered 
surface.  The  dark  is  often  used  in  polished  form. 

The  Barre  stone  is  perhaps  one  of  the  most  extensively  used 
in  the  United  States  and  some  large  pieces  have  been  taken  out. 
Professor  Perkins  mentions  one  that  was  95  feet  long,  45  feet 
wide  and  25  feet  thick.  Needless  to  say,  this  was  not  removed 
from  the  quarry  in  one  piece.  The  largest  finished  pieces  ever 
shipped  from  Barre  were  sent  to  Wheaton,  111.,  to  be  used  as 
roof  pieces  for  a  mausoleum.  Each  was  35  feet  long,  9  feet 
4  inches  wide,  and  i  foot  4  inches  thick.  Another  piece  quarried 
was  51  by  4  by  4  feet,  and  was  cut  into  a  shaft  which  is  now  in 
Greenwood  Cemetery,  Brooklyn,  N.  Y. 

Examples.  —  Calhoun  Monument,  Lexington,  Ky.;  Ohio  and  Iowa  State 
Soldiers'  Monuments,  Chattanooga,  Tenn.;  State  Soldiers'  Monument,  York,  Pa.; 
Hearn  Monument,  with  monolithic  spire,  53  by  4  by  4  feet,  Woodlawn,  N.  Y.; 
Gary  Mausoleum  with  roof  stones  of  the  " light,"  35  feet  by  9  feet  6  inches,  by 
i  foot  6  inches  each,  Wheaton,  111.;  First  North  Dakota  Soldiers'  Memorial,  St. 
Paul,  Minn.;  Cluett  Obelisk,  with  44-foot  shaft  and  pedestal,  Troy,  N.  Y.;  Holt- 
haus  Monument,  St.  Louis,  Mo.;  Columns  and  capitols  for  Flood  Mausoleum, 
San  Francisco,  Cal. 

Woodbury.  This  district  supplies  biotite  granites  of  more  or 
less  bluish  gray  color,  varying  from  dark  to  light  shades,  and  very 
fine  to  medium  texture. 

Examples.  —  Pennsylvania  State  Capitol,  Harrisburg,  Pa.;  Cook  County 
Court  House,  Chicago,  111.;  Syracuse  University  Library,  Syracuse,  N.  Y.;  Com- 
monwealth Trust  Co.,  Pittsburg,  Pa.;  Post  Office,  Des  Moines,  la. 

Windsor.  A  green  granite  found  on  Mount  Ascutney  and 
classed  mineralogically  as  a  hornblende-augite  granite.  It  is 
of  dark  olive-green  color  and  medium  texture.  The  stone  takes 
a  high  polish  and  shows  excellent  contrast  between  the  polished 


120  BUILDING   STONES  AND   CLAY-PRODUCTS 

and  hammered  surface;  indeed  it  is  one  of  the  handsomest 
granites  quarried  in  the  United  States. 

Examples.  —  Sixteen  polished  columns  (24  feet  9^  inches  by  3  feet  7  inches)  in 
Columbia  University  Library;  Monument  to  General  Gomez  in  Cuba;  a  die  in 
the  Bennington  monument;  thirty -four  large  columns  in  the  Bank  of  Montreal; 
columns  and  die  of  W.  C.  T.  U.  fountain,  Orange,  Mass.;  columns  for  interior  of 
Temple  of  the  Scottish  Rite,  Washington,  D.  C. 

MASSACHUSETTS. 

The  igneous  rocks  and  gneisses  quarried  in  Massachusetts, 
and  which  could  be  grouped  under  the  name  of  commercial 
granite,  present  considerable  variety  as  to  kind,  texture  and  color. 
The  important  constructional  ones  are  those  of  Milford,  Fall 
River,  New  Bedford  and  Rockport.  The  Quincy  granite  in 
polished  form  is  widely  known  because  of  its  value  for  monuments. 

The  most  important  granite  quarrying  centers  are  around 
Quincy,  Rockport,  Milford  and  Chester. 

Milford.  A  pink  or  pinkish  gray  or  even  greenish  gray  biotite 
granite,  with  spots  of  black  mica,  and  of  medium  to  coarse  texture. 
The  stone  has  a  slightly  gneissoid  appearance,  so  that  the  spots  are 
larger  when  the  granite  is  cut  parallel  to  the  planes  of  foliation  than 
when  the  faces  intersect  it  at  right  angles.  It  takes  a  good  polish 
and  is  extensively  used  for  exterior  and  interior  structural  work. 

Examples.  —  Eighty- four  3i-foot  sectional  columns  for  the  new  Pennsylvania 
Railroad  Station,  New  York  City;  Twelfth  Street  Station,  Illinois  Central  Rail- 
road, Chicago;  John  Hancock  Insurance  Company,  Boston,  Mass.;  Rochester  Safe 
Deposit  and  Trust  Company,  Rochester,  N.Y.;  Riggs  National  Bank,  Washington, 
D.  C.;  Interior  N.  Y.  Central  R.  R.  Station,  Albany,  N.  Y. 

Rockport.  The  quarries  are  on  Cape  Ann,  Essex  County, 
Massachusetts.  The  Rockport  granite  is  of  two  sorts,  viz.,  gray 
and  green.  The  gray  granite,  the  most  abundantly  known 
commercially,  is  a  hornblende  granite  of  medium  gray  color, 
spotted  with  black,  and  of  a  medium  to  coarse  but  even-grained 
texture.  It  is  said  to  be  a  hard  granite,  due  perhaps  to  its 
higher  percentage  of  quartz,  and  takes  a  good  polish. 

The  green  granite,  which  is  also  hornblendic,  is  of  a  somewhat 
dark,  olive-gray  color,  spotted  with  black.  The  texture  is  me- 
dium to  coarse,  though  even-grained.  This  stone,  though  dark 
gray  when  first  quarried,  becomes  greenish  after  an  exposure  of 


121 


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123 


IGNEOUS  ROCKS  (CHIEFLY  GRANITES)  AND  GNEISSES        125 

3  to  4  hours  to  the  rain.  It  also  fades  slightly  on  continued  ex- 
posure to  the  air.  The  stone  takes  a  high  polish,  but  shows  less 
contrast  between  hammered  and  polished  surface  than  the  gray. 

Examples.  —  Red:  Real  Estate  Trust  Company's  Building,  Philadelphia; 
American  Baptist  Publication  Building,  Philadelphia;  Interior  of  Suffolk  County 
Court  House,  Boston;  Siegel  Cooper  Company  Building,  New  York  City. 

Gray  Granite:  Boston  Post  Office;  Baltimore  Post  Office;  Suffolk  County 
Court  House,  Boston;  National  City  Bank  Building,  New  York  City;  Polished 
columns,  Madison  Square  Presbyterian  Church,  New  York  City. 

Green  Granite:  Madison  Avenue  Church  columns,  New  York  City;  Wain- 
scoting and  stairways  to  the  Towers  of  Philadelphia  Public  Buildings;  Logan 
Monument,  Chicago;  two  large  polished  bowls,  Plaza  Improvement,  Union 
Station,  Washington,  D.  C. 

Chester.  A  muscovite-biotite  granite,  of  bluish-gray  color  and 
somewhat  indefinite  texture.  It  takes  a  fair  polish  and  the 
hammered  surface  is  light.  Two  varieties,  the  Chester  dark  and 
Chester  light,  are  recognized.  It  is  used  chiefly  for  monuments, 
especially  in  Pennsylvania,  New  York  and  Michigan. 

Examples.  —  Doctor  Hoover  Monument  at  Chambersburg  and  McCormack 
Monument  at  Pittsburg,  Pa.;  W.  A.  Harder  Monument,  Hudson,  N.  Y. 

Quincy.  This  is  a  hornblende-pyroxene  granite.1  The  color 
is  medium  gray  or  bluish  or  greenish  or  purplish  gray,  to  a  very 
dark  bluish  gray,  and  dotted  all  over  with  black-appearing 
spots.  The  texture  is  medium  to  coarse,  but  even-grained. 

That  which  is  used  for  monumental  purposes  goes  under  the 
names  of  "medium  dark"  and  "  extra  dark."  The  "  light" 
Quincy  granite,  which  is  of  medium  gray  color,  is  considered 
second  grade  and  sells  for  rock  face  and  hammered  work. 

Other  and  cheaper  varieties  suitable  only  for  building  purposes 
are  the ' '  extra  light "  (pea  green) ,  the  pink  and  the  greenish  brown. 

Quincy  granite  is  noted  for  its  high  and  durable  polish,  and 
one  quarry  has  supplied  a  polished  ball  6  feet  6  inches  in  diameter. 

Examples.  —  Gore  Hall,  Harvard  University,  Cambridge,  Mass.;  Custom 
House,  New  Orleans,  La.;  Payne  Building,  Cleveland,  Ohio;  Polished  ball  of 
"dark"  granite,  6  feet  6  inches  diameter,  Rock  Island,  111.,  cemetery;  Bunker  Hill 
Monument,  Boston,  Mass.;  The  Long  Monument,  Mansfield,  Ohio. 

Classification  of  Massachusetts  Granites.  The  following 
classification  of  Massachusetts  granites  is  given  by  Dale,  the 
term  granite  being  used  in  the  commerical  sense. 

1  Strictly  speaking  the  minerals  are  riebeckite  and  aegirite. 


126 


BUILDING  STONES  AND   CLAY-PRODUCTS 


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IGNEOUS  ROCKS  (CHIEFLY  GRANITES)  AND  GNEISSES       127 


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128 


BUILDING  STONES  AND   CLAY-PRODUCTS 


RHODE  ISLAND. 


Westerly.  An  important  granite  industry  centers  at  this  town 
and  the  neighboring  one  of  Niantic.  The  "  Westerly  white 
statuary"  is  a  quartz  monzonite  of  more  or  less  pinkish  or  buff 
medium  gray  color,  and  fine  even-grained  texture.  The  "  Blue 
Westerly"  is  a  quartz  monzonite  of  more  or  less  bluish,  medium 
gray  color,  with  fine  black  particles  and  of  fine  even-grained 
texture.  "  Red  Westerly"  is  a  biotite  granite  of  reddish  gray 
color,  speckled  with  black,  and  of  even-grained,  medium,  inclin- 
ing to  coarse  texture. 

The  so-called  "  white"  and  the  "blue"  are  strictly  monumental 
granites,  the  former,  especially,  lending  itself  to  the  most  delicate 
carvings.  It  takes  a  high  polish  and  gives  good  contrast. 

The  blue  is  about  50  per  cent  coarser  than  white  and  polishes 
not  quite  as  well  but  gives  just  as  good  contrast. 

The  red  is  used  for  structural  work  only. 

Examples.  —  White  Westerly :  National  Monument,  Gettysburg,  Pa. ;  Antie- 
tam  Monument,  Md.;  J.  G.  Fair  Mausoleum,  San  Francisco.  Examples  of 
"Blue  Westerly":  Mutual  Insurance  Building,  Hartford,  and  building  of  same 
Company  in  Philadelphia.  Examples  of  "Red  Westerly":  Washington  Life 
Insurance;  American  Tract  Society  and  Travelers'  Insurance  Company  buildings, 
New  York  City. 

Dale  makes  the  following  classification  of  the  chief  commercial 
granites  of  Rhode  Island. 


Locality 

Trade  name 

Color 

Texture 

Constructional  

Westerly,  R.  I.  .  . 

.  Red  Westerly  

Reddish  gray  

Medium  to  coarse. 

Monumental  .  .  .  .  j 

Westerly,  R.  I.  .  . 
Westerly,  R.  I.  .  . 

Blue  Westerly.... 
White    and    pink 
Westerly. 

Blue  medium  gray. 
Pink  or  buff  me- 
dium gray. 

Fine. 
Extremely  fine. 

Inscriptional  < 

Westerly,  R.  I.  .  . 
Westerly,  R.  I.  .  . 

Blue  Westerly  
White    and    pink 
Westerly. 

Blue  medium  gray. 
Pinkish     or     buff 
medium  gray. 

Fine. 
Extremely  fine. 

Statuary  

Westerly,  R.I... 

Westerly      white 
statuary. 

Buff  medium  gray  . 

Extremely  fine. 

CONNECTICUT. 


The  granites  quarried  in  Connecticut  are  practically  all  granite- 
gneiss.  Some  of  these  are  of  the  same  mineral  composition  as  a 
normal  granite,  while  others  are  to  be  classed  as  quartz  mon- 
zonite or  mica-diorite  gneisses. 


PLATE  XXVI.—  Battle  Monument,  West  Point,  N.  Y.  Polished  shaft  of  Branford 
granite,  41  feet  6  inches  long  and  6  feet  in  diameter.  (Photo  loaned  by 
Norcross  Bros.) 

129 


IGNEOUS  ROCKS  (CHIEFLY  GRANITES)  AND  GNEISSES       131 

Branford  Township.  This  includes  the  well-known  Stony 
Creek  granite  gneiss,  and  is  denned  as  a  biotite  granite  gneiss  of 
medium  reddish  gray  color,  variable  medium  to  coarse  texture  and 
gneissoid  structure.  The  product  is  widely  used  for  buildings, 
bridges  and  monuments.  It  takes  an  excellent  polish. 

Examples.  —  South  Terminal  Station,  Boston;  Bessemer  Building,  Pittsburg, 
Pa.;  Newberry  Library,  Chicago;  polished  column  (41  feet  by  6  feet  2  inches  at 
base)  of  Battle  Monument,  West  Point;  obelisk  (45  feet  long)  at  Locks  Park, 
Sault  Ste.  Marie,  American  side;  Erie  County  Savings  Bank,  Buffalo,  N.  Y.  The 
Hoadley  Neck  quarries  have  supplied  stone  for  pedestals  of  Statue  of  Liberty,  New 
York  Harbor,  and  of  General  Anderson  Monument,  Fort  Sumter,  S.  C. 

Greenwich.  The  Greenwich  blue-black  granite  is  a  mica  dio- 
rite  gneiss  of  dark  bluish  gray  color,  being  darker  even  than 
the  Quincy  extra  dark,  and  coarsely  porphyritic  gneissose  texture. 
The  rock  is  very  tough  and  gives  a  brilliant  surface;  but  the 
effect  is  different,  depending  on  whether  the  grain  face  or  hard- 
way  face  is  exposed. 

The  chief  use  of  this  stone  is  for  buildings  and  massive  struc- 
tures. 

Examples.  —  Fort  Schuyler  on  Throgs  Neck,  Long  Island  Sound;  Episcopal 
Church,  Port  Washington,  Long  Island;  Catholic  Cathedral,  Green  Avenue, 
Brooklyn,  N.  Y. 

Waterford  Township.  A  quartz-monzonite,  known  as  "  Con- 
necticut white  "  granite,  is  quarried  south  of  Waterford  Station. 
This  rock  is  of  medium  buff  gray  shade,  and  fine,  even-grained 
texture,  and  is  a  fine-grained  monumental  and  inscriptional 
granite,  without  contrasts.  It  is  finer  than  the  Millstone  granite 
and  of  lighter  shade,  but  only  about  half  as  fine  as  the  "  Blue 
Westerly."  It  takes  a  high  polish. 

Examples.  —  Soldiers'  Monument,  Whitinsville,  Mass.;  Dudley  Celtic  Cross, 
Woodlawn  Cemetery,  N.  Y.;  Hoy  Mausoleum,  Mount  Moriah  Cemetery,  Phila- 
delphia; City  Deposit  Bank,  Pittsburg;  Basement  of  Clark  residence,  Riverside 
Drive,  New  York  City. 

Millstone.  The  stone  from  this  locality  is  a  quartz  monzonite, 
between  medium  and  dark  gray  smoke-colored,  and  even-grained 
granitic,  fine  texture.  It  is  a  brilliant  stone  for  inscriptional 
and  monumental  purposes  and  takes  a  high  polish.  It  hammers 
and  cuts  medium  gray  and  thus  affords  an  excellent  contrast 


132  BUILDING  STONES  AND   CLAY-PRODUCTS 

between  this  and  a  polished  surface.     The  texture  is  about  one- 
third  as  fine  as  that  of  the  coarser  "Blue  Westerly"  granite. 

Examples.  —  Saratoga  Monument,  interior  entrance,  and  all  but  upper  10  feet 
of  exterior;  base,  pedestal  and  cap  of  P.  T.  Barnum  Monument,  Bridgeport; 
George  W.  Childs  mausoleum,  Philadelphia. 

Groton.  The  several  quarries  at  this  locality  yield  a  quartz- 
monzonite,  of  fine,  granitic  texture,  and  greenish  color  of  slightly 
varying  shade.  It  is  a  monumental  granite,  somewhat  closely 
related  to  Blue  Westerly,  but  about  half  as  fine  in  texture.  The 
polish  between  the  cut  and  polished  face  is  marked,  a  char- 
acteristic of  all  monzonites. 

Examples.  —  William  Ledyard  Monument,  Ledyard  Cemetery,  Groton;  Ed- 
ward Newman  Obelisk,  Woodlawn  Cemetery,  New  York;  Rev.  Byron  A.  Woods 
Sarcophagus,  Forest  Hills  Cemetery,  Philadelphia;  Charles  Tyler  Statue,  Druid 
Hill  Ridge  Cemetery,  Baltimore;  Beckwith  and  Rogers  monuments,  Cedar  Grove 
Cemetery,  New  London. 

Among  the  other  important  quarries  in  Connecticut  are  those 
of  the  Glastonbury  gneiss  and  Sterling  granite  gneiss,  both  used 
for  curbing  and  trimming. 

A  list  of  all  the  Connecticut  quarries  by  Dale  and  Gregory  and 
the  kind  of  stone  which  they  produce  is  given  in  summarized 
form  below. 


IGNEOUS  ROCKS  (CHIEFLY  GRANITES)  AND  GNEISSES       133 


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136  BUILDING  STONES  AND  CLAY-PRODUCTS 

Market  Prices  of  Granites.  Dale  gives  the  following  prices, 
f.o.b.  per  cubic  foot  in  rough,  of  some  New  England  granites, 
they  being  the  ones  for  1906. 

Milford,  Mass.,  pink,  in  blocks  up  to  10  tons,  $0.60  to  $0.70.  Foundation  and 
bridge  rubble  work,  $0.25. 

Quincy,  light,  for  bases  and  hammered  work,  ordinary  sizes,  $0.50  to  $0.85. 
Extra  light,  for  bridge  work,  without  reference  to  size,  $0.35. 

Rockport,  gray,  ordinary  sizes  (3  to  15  feet  long,  i|  to  4  feet  wide,  and  i|  to 
3  feet  high),  best  quality,  $0.50. 

Concord,  blocks  under  9  feet  square  in  base,  $0.60. 

Redstone,  N.  H.,  red,  ordinary  sizes,  $0.40  to  $0.50. 

Milford,  N.  H.,  dimension  stone  in  blocks  up  to  100  cubic  feet,  $0.40. 

Westerly,  red,  ordinary  sizes,  $0.60. 

Quincy,  medium,  in  blocks  up  to  40  cubic  feet,  $i  to  $1.10;  40  to  55  cubic  feet, 
$1.15.  Dark,  in  blocks  up  to  40  cubic  feet,  $1.30  to  $1.35;  40  to  55  cubic  feet, 
$1.40.  Extra  dark,  in  blocks  up  to  40  cubic  feet,  $1.60. 

Becket  (Chester),  in  blocks  up  to  40  to  55  cubic  feet,  $1.30  to  $1.40. 

Redstone,  N.  H.,  green,  ordinary  sizes,  $0.65  to  $0.75. 

Milford,  N.  H.,  in  blocks  up  to  10  cubic  feet,  $0.75  to  $1.25,  averaging  $0.84. 

Westerly,  blue,  in  blocks  up  to  10  cubic  feet,  $1.10  to  $1.15.  Up  to  50  to  60 
cubic  feet,  $2.60  to  $2.75.  White  and  pink  statuary,  in  blocks  up  to  10  cubic  feet, 
$1.10  to  $1.25.  Up  to  50  to  60  cubic  feet,  $2.70  to  $3.25.  When  the  Milford, 
Mass.,  pink  is  ordered  finished  for  ornamental  work  the  following  prices  prevail: 
Rock-faced  ashlar  building  work,  $1.50.  Cut  building  work,  $3.50.  Polished 
building  work,  $6.  Cut  monumental  work,  $7.  Polished  monumental  work,  $10. 

Niantic,  Conn.,  "Golden  Pink,"  $1.25  to  $2.25,  from  5  to  30  cubic  feet. 

Dale l  also  quotes  the  following  prices  for  Connecticut  granites, 
the  price  unless  otherwise  specified  being  f.o.b.  cars,  per  cubic 
foot,  ordinary  sizes,  in  the  rough. 

Constructional  Granites.  Stony  Creek,  "Branford  Red,"  $0.75  for  dimension 
stock,  $0.53  for  random.  Hoadly  Neck,  $0.70.  Greenwich  (blue-black),  $0.45, 
boat,  for  dimension  stock;  $2.75,  boat,  per  long  ton,  for  large  random  ashlar;  $3.75, 
boat,  per  long  ton,  for  small  random  ashlar;  $1.75,  boat,  per  long  ton,  for  rubble. 
"Millstone  Granite,"  for  building,  in  pieces  up  to  30  cubic  feet,  averages  about 
$0.40,  f.o.b.  quarries. 

Monumental  Granites.  Waterford,  "Connecticut  White,"  $1.20  to  $1.80,  and 
"Millstone  Granite,"  $1.25,  cars  or  boat,  from  i  to  30  cubic  feet.  Niantic,  "Golden 
Pink,"  $1.25  to  $2.25,  from  5  to  30  cubic  feet. 

Curbing  and  Trimming  Granites.  Oneco  (Marriott),  $0.50;  Sterling  (Bennett), 
$0.35;  Glastonbury  (Belden),  curbing,  $0.45  per 'running  foot  at  quarry,  with 
cartage  of  10  miles  of  rail.  Seymour  (Holbrook),  $0.40  per  running  foot,  18  inches 
deep  and  four  inches  wiole.  Roxbury  (Mine  Hill),  $0.30  to  $0.40;  Waterford  (Flat 
Rock),  $0.45,  delivered  in  New  London. 

1  U.  S.  Geol.  Surv.,  Bull.  484,  p.  127,  1911. 


IGNEOUS  ROCKS  (CHIEFLY  GRANITES)  AND  GNEISSES       137 


Miscellaneous.     Guilford  (Sachem  Head)  breakwater  granite  $0.999  Per 
ton  dumped  at  breakwater,  12  miles  from  quarry,  minimum  weight  of  blocks  500 
pounds.     Greenwich  riprap,  per  long  ton,  boat,  $1.25. 


NEW  YORK. 

This  state  is  of  little  importance  as  a  granite  producer,  and 
the  occurrences  are  confined  to  the  borders  of  the  Adirondack 
Mountain  region,  including  Jefferson  County,  and  to  south- 
eastern New  York.  Among  the  causes  assigned  for  the  lack  of 
development  of  the  New  York  granites  are,  less  favorable  trans- 
portation facilities,  lack  of  name  and  irregularity  of  deposits. 

Along  the  St.  Lawrence  River  a  medium-grained  pink  granite 
of  ornamental  character  and  capable  of  good  polish  has  been 
worked  at  Pic  ton. 

Examples.  —  New  wing,  American  Museum  of  Natural  History,  New  York 
City;  First  National  Bank,  Clayton,  N.  Y. 

A  deep  red,  coarsely  crystalline  granite,  capable  of  taking  a 
high  polish,  has  been  quarried  on  Grindstone  Island,  Jefferson 
County.  It  is  of  great  beauty  and  ornamental  value. 

Another  good  stone  occurs  near  Ausable  Forks.  This  rock  is 
of  a  sombre  green  color,  takes  a  handsome  polish  and  is  well 
adapted  for  monumental  and  building  work. 

The  coarse-grained  granite,  and  the  gray  gneisses  of  West- 
chester  and  Putnam  counties  have  been  quarried  locally.  A 
granite  occurring  near  Peekskill,  and  known  as  Mohegan  granite, 
shows  a  yellowish  tint.  It  has  been  used  in  the  construction  of 
St.  John  the  Divine  Cathedral  in  New  York  City. 

NEW  JERSEY. 

Gneisses  and  granites  are  found  in  the  Highland  area  of  the 
state.  This  belt  is  from  10  to  20  miles  wide,  and  Jenny  Jump 
Mountain  near  Belvidere  and  Pochuck  Mountain  near  Franklin 
Furnace  are  its  northwestern  outposts. 

The  rocks  of  the  Highlands  are  chiefly  light  colored  aggregates 
of  feldspar  and  quartz  which  are  to  be  classed  as  gneisses  or 
granite  gneisses. 


138  BUILDING   STONES  AND   CLAY-PRODUCTS 

The  following  occurrences  may  be  mentioned. 

Pompton  Pink  Granite.  A  coarse-grained  pink  granite,  with 
yellowish  green  mottlings  from  the  region  around  Pompton.  It 
may  contain  gneiss  inclusions.  The  texture  is  variable,  varying 
from  medium  fine  to  very  coarse  grained,  and  there  is  a  corre- 
sponding variation  in  proportions  of  pink,  white  and  green  colors. 
Some  dark  brown  mica  is  present. 

Examples.  —  St.  Paul's  Church  at  Paterson,  N.  J. 

Dover  Light  Gray  Granite  Gneiss.  This  is  light  gray  to  green- 
ish in  color,  medium-grained  texture,  and  contains  feldspar, 
quartz  and  greenish  black  hornblende  in  variable  proportions. 

Examples.  —  First  M.  E.  Church,  Dover. 

Cranberry  Lake  White  Granite  Gneiss.  A  fine-grained  white 
to  very  light  gray  granite,  sprinkled  with  small  pink  garnets. 
Gneissic  structure  scarcely  noticeable.  A  gray  granite  gneiss  is 
also  obtained  here. 

German  Valley  Gray  Granite.  A  medium-grained  rock  with 
orthoclase,  plagioclase,  quartz,  and  scattered  dark  green  horn- 
blende. It  may  also  be  well  adapted  to  monumental  work. 

Examples.  —  Brainerd  Hall,  Lafayette  College,  and  Blair's  Hall,  College  Hill, 
Easton,  Pa.;  Carnegie  Bridge,  Princeton,  N.  J. 

Trap  Rock.  Several  belts  in  northeastern  New  Jersey.  Its 
main  use  is  for  foundations  and  concrete.  The  sombre  color  is 
against  its  extensive  use. 

Coarse-grained  granitic  types,  as  those  found  in  Rocky  Hill, 
Sourland  Mountain  and  part  of  the  Palisades,  could  be  used  for 

building. 

MARYLAND. 

The  granites  and  gneisses  of  Maryland  are  all  found  within 
the  Piedmont  plateau  province,  and  while  granite  has  been 
developed  in  about  fifteen  areas,  there  are  but  five  of  importance, 
viz.,  Port  Deposit,  French  town,  Ellicbtt  City,  Woodstock  and 
Guilford. 

Mineralogically  the  Maryland  granites  can  be  divided  into 
three  groups,  as  follows: 

i.  Biotite  granite;  Port  Deposit,  Frenchtown,  Woodstock, 
Dorsey's  Run,  Texas,  Ellicott  City,  Ilchester. 


•c 


£?i        ,s/»v.* 


IGNEOUS  ROCKS  (CHIEFLY  GRANITES)  AND  GNEISSES       141 

2.  Muscovite-biotite  granite;  Guilford. 

3.  Hornblende-biotite  granite ;    Garrett  Park,  Rowlands ville. 
Texturally  the  granites  of  this  state  are  divisible  into  two 

groups,  viz.,  granites  proper  and  gneisses. 

The  more  important  ones  are  referred  to  below. 

Granites,  Port  Deposit.  This  is  the  best-known  Maryland 
granite,  and  is  quarried  on  the  Susquehanna  River,  about  three 
miles  above  Havre  de  Grace.  (See  Plate  XXVIII.) 

It  is  a  light,  bluish  gray  granite  gneiss,  of  medium  texture, 
whose  foliation  is  emphasized  by  the  black  mica  scales.  The 
stone  darkens  on  exposure  due  to  the  accumulation  of  dust  on  the 
surface.  It  is  extensively  used  for  building  in  the  southern  states. 

Examples.  —  Mount  Royal  Station,  Baltimore,  Md.;  Maryland  Penitentiary, 
Baltimore,  Md.;  Catholic  University  Buildings,  Washington,  D.C.;  Girls'  High 
School,  and  St.  Paul's  Presbyterian  Church,  Philadelphia,  Pa.;  St.  Lawrence, 
R.  C.  Church,  Pittsburg,  Pa.;  St.  Patrick's  Church,  Erie,  Pa. 

Ellicott  City.  On  the  Baltimore  County  side  the  quarries  yield 
a  biotite  granite  of  medium  dark  blue-gray  color  and  medium 
porphyritic  texture.  It  is  somewhat  foliated.  On  the  Howard 
County  side,  the  granite  is  a  porphyritic  biotite  granite  of  dark 
gray  color,  medium  grain  and  massive  character. 

Examples.  —  This  stone  has  been  much  used  around  Baltimore,  the  cathedral 
in  that  city  being  constructed  of  it. 

Guilford.  This  is  one  of  the  most  attractive  of  .the  Maryland 
granites.  It  is  a  muscovite-biotite  granite  and  varies  from  a 
coarse-grained  rock  of  red  color,  through  a  medium-grained 
reddish  gray  to  fine-grained  medium  gray.  The  last  named  is 
the  most  extensively  quarried  and  is  marketed  chiefly  in  Mary- 
land and  Pennsylvania. 

Woodstock.  A  biotite  granite  of  medium  gray  color  and 
medium  grain.  The  slightly  greater  amount  of  biotite  makes  it 
a  little  darker  than  the  Guilford  and  slightly  coarser  in  texture. 

The  product  is  used  chiefly  for  general  building  in  both  the 
rough  and  dressed  states.  Other  uses  are  for  monuments,  paving 
blocks,  some  curbing  and  concreting. 

Examples.  —  Custom  House,  Baltimore,  Md.;  Arsenal  Building,  Philadelphia, 
Pa.;  Rittenhouse  Building,  Pittsburg,  Pa.;  Willard  Hotel,  Washington,  D.  C.; 
German  Savings  Bank,  Baltimore,  Md. 


142  BUILDING   STONES  AND   CLAY-PRODUCTS 

Frenchtown  Area.  This  is  a  biotite  granite  gneiss  of  gray 
color  and  medium  grain.  It  is  a  shade  darker  than  the  Port 
Deposit  granite  and  is  used  chiefly  for  pavers. 

Gneisses.  The  Baltimore  gneiss  forms  several  areas  along  the 
eastern  slope  of  the  Piedmont  region  between  the  Susquehanna 
and  the  Potomac  rivers.  Extensive  quarries  have  been  worked 
for  many  years  on  the  north  and  west  sides  of  the  city  of  Balti- 
more, around  Jones  Falls  and  Gwynn  Falls. 

It  is  a  quartz-feldspar-mica  gneiss,  of  well-banded  character, 
but  variable  texture  and  color.  Bluish  gray  is  the  commonest 
color.  The  product  is  used  chiefly  in  Baltimore  for  paving, 
curbing  and  crushed  stone. 

VIRGINIA. 

Granites  are  limited  to  the  crystalline  area,  which  extends 
eastward  from  the  Blue  Ridge  to  the  western  margin  of  the 
Coastal  Plain,  and  they  comprise  massive  and  gneissic  types. 
The  latter  especially  have  a  wide  distribution  over  the  Piedmont 
region  and  they  form  one  of  the  principal  types  of  rock. 

The  chief  areas  are:  (i)  the  Petersburg  area;  (2)  the  Rich- 
mond area;  and  (3)  the  Fredericksburg  area. 

In  these  most  important  areas  the  granites  are  mixtures  of 
quartz,  feldspar  and  biotite,  but  more  or  less  muscovite  is  also 
usually  present.  In  addition  to  the  principal  feldspar  or  ortho- 
clase,  microcline  and  plagioclase  occur  in  widely  varying  amounts. 

The  properties  of  the  granites  in  the  three  important  areas 
above  mentioned  are  as  follows : 

Petersburg  Area.  A  biotite  granite  of  medium  texture  and 
gray  color,  adapted  to  constructional  and  monumental  work. 

Richmond  Area.  This  is  the  largest  producing  area  in  the 
state,  a  number  of  quarries  being  located  in  immediate  vicinity 
of  Richmond  and  Manchester.  These  are  biotite  granites  from 
fine  to  medium  texture  and  light  to  dark  gray  color.  An  ex- 
ceptionally beautiful  type  is  the  porphyritic  granite  occurring 
near  Midlothian,  thirteen  miles  west  of  Richmond. 

Two  grades  of  granite  are  recognized :  one  a  fine-grained,  dark 
blue-gray  stone,  extensively  used  as  monumental  stock ;  the  other 


PLATE  XXVIII,  Fig.  i. — Port  Deposit,  Maryland,  gneissic  granite  with  face  cut 
at  right  angles  to  banding. 


PLATE  XXVIII,  Fig.  2.  —Port  Deposit,  Maryland,  gneissic  granite  with  face  cut 
parallel  to  the  banding. 

143 


IGNEOUS  ROCKS  (CHIEFLY  GRANITES)  AND  GNEISSES        145 

a  lighter  gray  rock,  well  adapted  to  building  purposes.  The 
former  takes  high  polish  and  gives  strong  contrast  between 
polished  and  hammered  surface. 

Examples.  —  State,  War  and  Navy  Building,  Washington,  D.  C.;  St.  Andrews 
Church  and  Union  Theological  Seminary,  Richmond,  Va. 

Fredericksburg  Area.  Two  types  of  granite  are  obtainable  (i) 
a  very  light  gray  medium-textured,  muscovite  granite,  and,  (2)  a 
dark  blue-gray,  very  fine  textured  biotite  granite,  identical  with 
that  quarried  in  the  Richmond  area  and  used  for  monumental 
stock. 

Other  Localities.  Gneisses  have  been  quarried  in  the  region 
around  Lynchburg  and  used  locally.  They  are  also  worked  at  a 
few  other  localities. 

A  yellow,  green  and  pink  epidote  granite,  known  as  unakite, 
is  found  at  two  localities,  viz.,  Milams  Gap  in  the  Blue  Ridge 
near  Luray  and  Troutdale,  Grayson  County.  It  is  moderately 
coarse,  but  shows  an  irregular  crystallization  of  red  feldspar, 
quartz  and  green  epidote. 

Trap  rock  or  diabase  is  rather  widely  distributed  over  parts 
of  the  Blue  Ridge  and  the  crystalline  area  in  Virginia,  but  only 
a  few  quarries  have  been  opened  in  it,  the  principal  ones  being  in 
Loudoun,  Fauquier  and  Culpepper  counties.  The  stone  has 
been  used  for  paving  purposes  and  bridge  abutments  only. 

NORTH  CAROLINA. 

Granites  are  distributed  over  about  one-half  the  total  area  of 
the  State,  but  quarries  have  been  operated  at  only  a  few  localities. 

The  granites  and  gneisses  occur  in  the  coastal  plain,  the  Pied- 
mont plateau  and  the  Appalachian  Mountains  district,  but  the 
larger  part  of  the  granites  are  comprised  within  the  limits  of  the 
Piedmont  plateau  region. 

The  North  Carolina  granites  show  a  mineralogical  resemblance 
to  those  of  the  other  states  in  the  southern  Appalachian  region. 
That  is  to  say,  they  are  mixtures  of  feldspars  (plagioclase  usually 
in  excess),  and  quartz,  with  biotite  as  the  third  essential  mineral 
in  the  most  important  areas.  They  are  characterized  by  a 


146  BUILDING   STONES  AND   CLAY-PRODUCTS 

strong   development   of   vertical   joints,    the   most   noteworthy 
exception  being  the  granite  of  Mount  Airy. 

Watson  makes  the  following  divisions  on  a  mineralogic  basis: 

1.  Biotite  granite,  with  or  without  muscovite,  and  including  most  of  the  areas 

of  the  state,  such  as  Mount  Airy,  Dunns  Mountain,  and  Greystone. 

2.  Hornblende  biotite  granite,  including  the  granites  of  northern  and  southern 

Mecklenburg  County. 

3.  Muscovite  granite,  with  or  without  biotite,  as  Warren  Plains  in  Warren 

County. 

4.  Epidote  granite,  from  Madison  County. 

Knots  are  entirely  absent  in  some  quarries  and  occur  only 
here  and  there  in  others,  but  in  a  few  they  are  so  abundant  as  to 
disfigure  the  granites  for  some  of  the  higher  grades  of  work. 

Most  of  the  quarries  show  pegmatite  dikes,  and  in  some  these 
are  so  abundant  that  dimension  stone  is  difficult  to  obtain. 
This  is  especially  true  of  the  Raleigh  City  quarries,  where  hardly 
a  block  entirely  free  from  quartz  feldspar  dikes  can  be  extracted. 

The  bulk  of  the  North  Carolina  granites  are  of  even-granular 
character  and  range  from  massive  to  partly  schistose  rocks  of 
fine  to  medium  texture,  rarely  coarse.  The  color  is  pink  to 
gray,  but  prevailing  light  to  medium  dark  gray. 

The  North  Carolina  granites  may  be  grouped  on  a  textural 
basis  as  even-granular  granites  and  porphyritic  granites. 

Even-granular  Granites.  These  have  a  wide  distribution  and 
include  the  bulk  of  the  North  Carolina  granites.  Those  in  the 
several  topographic  provinces  may  be  briefly  referred  to. 

Coastal  Plain.  Granites  are  found  at  several  localities,  espe- 
cially in  Wilson,  Edgecomb  and  Nash  counties,  east  of  Raleigh. 
The  openings  are  small  and  made  for  local  use  only. 

Piedmont  Plateau  Region.  This  is  commercially  the  most 
important  area  in  North  Carolina  and  contains  several  granite 
belts  approximately  parallel  to  one  another.  The  granites  are 
usually  biotite  bearing,  with  additional  hornblende  in  several  of 
the  areas,  but  muscovite  is  rare.  They  are  usually  some  shade  of 
gray,  but  occasionally  pink  is  the  characteristic  color. 

The  stone  is  often  of  good  quality,  readily  accessible  and 
easily  worked.  Some  of  the  more  important  areas  are  referred 
to  below. 


J  /   *  1  »    '•     -.111? 

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IGNEOUS  ROCKS  (CHIEFLY  GRANITES)  AND  GNEISSES        149 

Grey  stone.  This  is  one  of  the  best-known  North  Carolina 
granites  and  has  been  worked  for  a  long  time.  It  has  been  used 
mostly  for  street  purposes,  in  the  form  of  blocks  for  coping  and 
bridges,  and  to  a  less  extent  as  a  building  stone.  The  stone  is  a 
biotite  granite  of  gray  to  pinkish  gray  color,  fine 'to  medium 
grain  and  schistose  structure. 

Raleigh.  This  is  a  biotite  granite  of  medium  gray  color  and 
even,  fine  grain,  with  a  somewhat  schistose  structure.  It  is 
used  chiefly  for  common  building  and  curbing. 

Wise.  A  muscovite-biotite  granite  of  medium  light  gray  color, 
medium  grain  and  massive  character.  Is  quarried  for  general 
dimension  work. 

Rowan  County.  One  of  the  most  important  granite  areas  in 
the  state  lies  near  Salisbury,  Rowan  County,  where,  beginning 
about  four  miles  east  of  Salisbury,  it  extends  southward  for  more 
than  twelve  miles.  The  stone  has  been  widely  used  in  North 
Carolina  and  adjoining  states.  Both  a  light  gray  nearly  white 
biotite  granite  and  a  pink  one  of  uniform  color  and  texture  are 
quarried. 

Both  kinds  occur  at  Dunn's  Mountain,  four  miles  east  of 
Salisbury,  and,  while  there  is  no  difference  in  durability,  the  pink 
is  more  desirable  for  certain  classes  of  high-grade  work. 

Some  of  the  pink  granite  is  of  a  beautiful  color  and  takes  a 
high  polish. 

Examples.  —  Catholic  University,  Washington,  D.  C.;  New  Municipal  Court 
Building,  Washington,  D.  C.  The  pink  granite  is  in  much  demand  in  Chicago  and 
other  northern  and  central  cities  for  monumental  stock. 

Mount  Airy.  The  stone  quarried  here  is  a  very  light  gray 
biotite  granite  of  medium  texture,  and  contains  no  visible  in- 
jurious minerals.  It  is  excellently  adapted  to  general  construc- 
tional work,  but  not  good  for  monumental  work  where  contrast 
between  hammered  and  polished  surface  is  desired. 

Examples.  —  Dry  dock  at  Newport  News,  Va. ;  Union  Trust  Building,  Washing- 
ton, D.  C.;  third  story  of  New  National  Museum  Building,  Washington,  D.  C. 

Porphyritic  Granites.  These  occur  at  many  points  in  the  same 
regions  as  the  even-granular  ones,  but  they  are  not  regularly 
quarried. 


150  BUILDING  STONES  AND   CLAY-PRODUCTS 

An  exceedingly  interesting  and  beautiful  rock  is  a  quartz 
porphyry  which  occurs  near  Charlotte,  Mecklenburg  County. 
It  is  a  dense,  hard,  tough,  compact,  finely  crystalline  rock  of 
nearly  white  color,  with  faint  greenish  tinge  in  places.  The  stone 
is  penetrated  by  long  parallel  streaks  or  pencils  of  black  color. 
When  broken  at  right  angles  to  the  streaks  the  surface  is  dotted 
with  rounded  irregular  spots,  but  when  cut  along  the  streaks 
they  show  a  curious  branching  pattern.  (Plate  XXIX.) 

The  rock  takes  an  excellent  polish  and  could  be  used  with 
splendid  effect  for  inlaid  work. 

Miscellaneous  Rocks.  West  of  Lexington,  Davis  County, 
there  occurs  an  orbicular  gabbro-diorite.  It  is  of  dark  color,  with 
a  greenish  cast,  and  shows  a  curious  mottled  appearance  due  to 
numerous  dark-green  areas  of  hornblende,  ranging  from  an  eighth 
inch  to  several  inches  in  diameter,  set  close  together,  and  the 
interstices  filled  with  white  feldspar.  The  effect  produced  on  a 
polished  surface  of  the  stone  is  at  once  unique  and  beautiful.  It 
seems  to*be  a  neglected  ornamental  stone.  (Plate  XXIX.) 


SOUTH   CAROLINA. 

The  granitic  rocks  of  this  state  occur  in  a  roughly  triangular 
area,  lying  between  the  fall  line  on  the  southeast,  the  Savannah 
River  and  Georgia  on  the  southwest,  and  the  North  Carolina 
boundary  on  the  north. 

The  chief  producing  areas  are  Columbia  in  Richland  County; 
Lexington,  Lexington  County;  Edgefield,  Edgefield  County; 
Winnsboro,  Fairfield  County;  Heath  Springs,  Lancaster  County; 
Beverly,  Pickens  County. 

In  common  with  those  of  the  southeastern  Atlantic  States, 
the  South  Carolina  granites  vary  in  structure  from  massive  to 
gneissose,  and  in  texture  from  even  granular  to  porphyritic. 

The  South  Carolina  granites  are,  with  one  exception,  biotite 
granites,  even  granular,  fine-  to  medium-grained  (rarely  coarse- 
grained), and  usually  some  shade  of  gray. 

Porphyritic  ones  are  common,  but  less  numerous  than  in 
Georgia  and  North  Carolina. 


PLATE  XXIX,  Fig.  i.  —  Leopardite  from  North  Carolina.     (T.  L.  Watson,  photo.) 


PLATE  XXIX,  Fig.  2.— Orbicular  gabbro  from  North  Carolina.     (U.  S.  Geol.  Surv.) 


IGNEOUS  ROCKS  (CHIEFLY  GRANITES)  AND  GNEISSES        153 

Of  the  granite  gneisses,  those  quarried  by  the  Grenville 
Granite  Company  in  Pickens  County  are  most  typical.  They 
resemble  closely  the  contorted  biotite  granite  gneiss  of  Lithonia, 
Ga. 

Pegmatite  veins  are  common  in  some  of  the  quarries,  but  are 
not  usually  large,  while  quartz  veins  are  exceptional.  Vertical 
joints  are  present,  but  horizontal  joints  are  less  commonly  de- 
veloped than  in  the  granite  quarries  of  the  other  southern  states. 

Among  the  best-known  South  Carolina  granites  are  those  of 
the  Rion  and  Anderson  quarries  of  the  Winnsboro  Granite  Cor- 
poration. 

The  Rion  granite  is  a  gray  stone,  used  chiefly  for  building 
stone,  while  the  Anderson  granite  is  a  blue-gray  used  exclusively 
for  monuments. 

The  working  qualities  of  the  Rion  granite  are  excellent  and  it 
is  splendidly  adapted  to  architectural  work,  for  which  it  has  had 
an  extensive  sale,  as  indicated  in  the  following  list  of  prominent 
structures  in  which  it  has  been  used: 

Examples.  —  United  States  Court  House  and  Post  Office  Buildings,  Wilming- 
ton, N.  C.;  Asheville,  N.  C.;  and  Opelousas,  Ala.  Post  Offices,  Charleston,  S.  C.; 
Durham,  N.  C.;  Chillicothe,  Ohio;  Traverse  City,  Mich.;  Florence,  S.  C.,  and 
Charlottesville,  Va.  Fidelity  Title  and  Trust  Company  Building  and  Hussey 
Building,  Pittsburg,  Pa.;  New  Land  Title  and  Trust  Company  Building,  Phila- 
delphia, Pa.;  United  States  Custom  House,  Baltimore,  Md.;  Building  No.  i,  com- 
mandant's office,  Navy  Yard,  Charleston,  S.  C.;  Fairmount  Trust  Company,  Fair- 
mount,  W.  Va.;  and  Empire  Bank  Building,  Clarksburg,  W.  Va. 

In  addition  to  its  principal  use  in  architectural  work,  the  product  is  used  for 
monument  bases.  The  dry  docks  at  Charleston,  S.  C.,  were  built  of  this  stone, 
200,000  cubic  feet  being  used. 

The  Anderson  stone  is  dark  blue-gray  in  color  and  fine  grained. 
It  is  closely  similar  to  dark  blue-gray  granites  at  Oglesby,  Ga.; 
Heath  Springs,  S.  C.;  Richmond  and  Fredericksburg,  Va. 

Heath  Springs.  This  rock  is  a  biotite  granite  of  uniform  dark 
gray  color  and  fine  grain.  It  takes  a  high  polish,  and  is  adapted 
to  high-grade  monumental  stock,  for  which  it  is  exclusively  used. 
The  product  has  been  shipped  as  far  as  Brooklyn,  N.Y.,  Den- 
ver, Colo.,  and  Portland,  Ore. 

Columbia.  Several  quarries  are  located  near  here.  It  is  a 
biotite  granite  of  gray  color  and  fine  to  coarse  grain,  or  again  of 


154  BUILDING   STONES  AND   CLAY-PRODUCTS 

reddish  gray  color  and  medium  grain,  with  pronounced  porphy- 
ritic  tendency.     The  product  is  used   chiefly  for    rough    and 

crushed  stone. 

GEORGIA. 

Granites  of  excellent  quality  and  some  variety,  well  suited 
for  general  building  and  monumental  work,  have  long  been 
known  in  Georgia,  although  for  many  years  the  light  gray  Stone 
Mountain  granite  was  the  only  one  known  beyond  the  limits  of 
the  state. 

The  granites  occur  in  the  Piedmont  region  which  occupies  the 
middle  northern  portion  of  the  state,  but  while  granites  and 
granite  gneisses  are  widely  distributed  throughout  this  area,  only 
four  counties  are  important  producers,  and  of  these  DeKalb  is 
the  most  important. 

The  five  producing  areas  are  as  follows : 

1.  Elberton-Oglesby-Lexington  Area.     In  the  Oglesby-Lexing- 
ton  district  we  have  a  biotite  granite  of  dark  blue-gray  color,  and 
fine,  even  grain.     It  is  fairly  uniform  in  texture  and  color,  works 
well  under  the  hammer,   and  takes  an  excellent  polish  with 
striking  contrast  between  cut  and  polished  surface. 

The  uniformity  of  color  and  texture,  fineness  of  grain,  freedom 
from  imperfections  and  blemishes,  together  with  great  strength 
and  durability,  rank  it  high  as  a  monumental  stone.  The  Elber- 
ton-Echols  Mill  district,  although  continuous  with  the  preceding, 
is  a  biotite  granite  of  light-gray  color  and  medium,  even-grained 
texture.  The  stone  is  well  suited  to  all  grades  of  constructional 
work. 

2.  Lithonia-Conyers-Lawrenceville  Area.     This  represents  one 
of  the  two  principal  areas  of  granite  gneiss,  the  other  being  the 
Odessa-Mountville  area.     In  the  former  the  principal  quarrying 
center  is  Lithonia.     The  rock  is  hard,  firm,  close  textured,  fine- 
grained  biotite   granite   gneiss,    of   medium-gray   color.      The 
granite  is  used  chiefly  for  paving  and  curbing. 

3.  Fairburn-Newman-Greenmlle  Area.     This  region  supplies  an 
even-granular  massive  biotite  granite  of  two  varieties.     One  is  a 
medium  gray,  fine- textured  rock;   the  other  is  a  dark  bluish  gray 
granite  of  more  coarsely  crystalline  texture  and  darker  color. 


IGNEOUS  ROCKS  (CHIEFLY  GRANITES)  AND  GNEISSES       155 

The  stone  is  admirably  adapted  for  general  building  and  con- 
structional work  and,  in  places,  for  monumental  stock. 

4.  Stone  Mountain  Area.     Stone  Mountain  is  an  elliptical 
ridge  of  granite,  686  feet  high  and  7  miles  in  circumference, 
rising  above  the  surrounding  plain.     The  area  yields  a  biotite- 
bearing  muscovite  granite  of  uniformly  light  gray  color  and 
moderately  fine-grained  but  variable  texture. 

The  stone  is  extensively  used  for  general  building  purposes, 
and  has  been  marketed  in  the  principal  towns  and  cities  of  the 
South  and  West.  Its  light  color  makes  it  undesirable  for  monu- 
mental stock. 

5.  Sparta  Area.     There  are  a  number  of  porphyritic  granites 
known  in  Georgia,  but  except  in  the  Sparta  area  they  have  been 
very  sparingly  quarried,  and  then  only  to  supply  a  strictly  local 
demand. 

The  Sparta  stone  is  a  prevailingly  coarse-grained,  medium-gray 
porphyritic  biotite  granite,  which  appeared  to  be  used  chiefly 
for  paving  purposes. 

ALABAMA. 

The  crystalline  rocks  of  Alabama  occupy  a  triangular  area  in 
the  northeastern  part  of  the  state. 

Granite  of  good  quality  occurs  in  considerable  quantity  at  a 
few  localities  in  the  crystalline  area  of  Alabama,  but  no  regular 
quarries  have  been  opened.  Granite  gneisses  are  also  known. 

WISCONSIN-MINNESOTA   AREA. 
Wisconsin. 

The  igneous  rocks  quarried  in  Wisconsin  are  mainly  granite 
and  rhyolite,  and  the  purposes  for  which  they  are  quarried  are 
monumental,  building  and  rock  construction. 

According  to  Buckley  the  Wisconsin  quarries  furnish  thirteen 
different  colored  and  textured  granites.  These  include  all  colors 
from  brilliant  red  to  dark  gray,  and  all  textures  from  very  fine- 
grained to  coarsely  porphyritic  ones. 

The  most  important  ones  are  referred  to  below. 

Montello.  A  dense  fine-grained  granite  of  red  color,  or 
sometimes  a  grayish  red.  There  is  no  regularity  in  occurrence 


156  BUILDING   STONES  AND   CLAY-PRODUCTS 

of  the  two  types.  Black  and  white  streaks  sometimes  traverse 
the  stone  and  have  to  be  avoided  for  monumental  work.  The 
granite  takes  an  excellent  polish,  and  the  hammered  surface  is 
much  lighter.  It  is  a  stone  of  exceptional  beauty,  and  is  a 
valuable  monumental  stone. 

Examples.  —  Wisconsin  Soldiers'  Monument,  Gettysburg,  Pa.;  Sarcophagi  in 
Gen.  Grant's  Tomb,  New  York  City;  Wisconsin  Monuments,  National  Park, 
Vicksburg,  Miss. 

For  structural  work  it  has  been  used  in  Herald  Building,  Chicago,  and  several 
private  residences. 

Berlin.  The  stone  is  known  as  quartz  porphyry,  but  is 
properly  a  rhyolite.  It  is  very  compact,  of  dense  and  uniform 
texture.  The  color  in  general  is  grayish  black,  but  often  shows 
a  pinkish  tinge  from  large  feldspars  scattered  through  the  ground 
mass.  Occasional  small,  black  streaks  which  mar  the  ordinarily 
uniform  color  occur  in  the  rock. 

Degree  of  polish  depends  on  surface  polished.  The  "run" 
and  "head"  surfaces  take  a  very  excellent  finish,  but  the  rift 
side  does  not.  The  polished  surface  is  dark  grayish  black,  and 
the  hammered  face  light  bluish  gray. 

It  is  a  strong,  durable  monumental  stone,  and  the  only  injuri- 
ous characteristics  are  the  occasional  occurrence  of  incipient 
cracks,  black  streaks  and  veins  of  white  quartz. 

Examples.  —  Used  in  Science  Hall,  Madison,  Wis.,  and  Bartlett  Building, 
Chicago,  111.  Many  paving  blocks  are  made  from  it. 

Warren.  This  stone,  which  is  quarried  about  twelve  miles 
northeast  of  Berlin,  is  known  as  Waushara  granite.  The  color 
is  deep  pink,  but  lighter  than  Montello,  on  both  the  hammered 
and  polished  surfaces.  It  takes  a  fine  polish,  but  the  contrast 
between  hammered  and  polished  surface  is  not  extra  strong,  and 
is  fine  grained.  It  consists  essentially  of  quartz  and  feldspar, 
these  making  up  90  per  cent  of  the  rock,  while  hornblende  and 
muscovite  are  subordinate.  The  stone  is  used  mainly  for 
monumental  work  and  paving. 

Waupaca.  A  beautiful  porphyritic  granite  in  several  colors, 
viz.,  black  and  pink,  called  gray;  green  and  pink,  called  red. 
Pink  feldspars  predominate  in  nearly  all  varieties. 


IGNEOUS  ROCKS  (CHIEFLY  GRANITES)  AND  GNEISSES       157 

The  rock  consists  mainly  of  large  feldspars  between  which  are 
disseminated  small  crystals  of  feldspar,  quartz,  hornblende, 
biotite,  chlorite  and  epidote. 

Flesh-colored  feldspar  contributes  a  reddish  tinge  to  the  rock, 
while  the  biotite  and  hornblende  are  the  sources  of  the  black 
color.  The  green  color  is  due  to  epidote  and  chlorite. 

In  general,  it  takes  excellent  polish,  the  red  taking  better  than 
gray.  The  hammered  surface  is  pinkish  red  color,  but  the 
contrast  is  not  very  sharp.  Owing  to  coarse  feldspars,  some 
difficulty  is  experienced  in  dressing  sharp  corners.  It  is  best 
suited  for  inside  work. 

Examples.  —  Omaha  Bee  Building,  Omaha,  Neb.;  Gateway  to  Lake  View 
Cemetery,  Minneapolis,  Minn.;  Wisconsin  State  Soldiers  Monument  at  Chicka- 
mauga,  Tenn. 

Wausau.  This  is  a  medium  coarse  grained,  reddish  brown, 
red  or  gray  granite,  with  a  little  biotite  and  hornblende,  which 
takes  a  high  polish  and  gives  good  contrast  between  the  ham- 
mered and  polished  surface.  It  is  used  for  monumental,  orna- 
mental and  constructional  purposes. 

Example.  —  Marathon  County  Bank,  Wausau. 

Amberg.  Fine-grained  gray  granite  mainly  for  ordinary  con- 
structional work. 

Example.  —  Chicago  Historical  Society,  Chicago,  111. 

MINNESOTA. 

The  two  chief  granite-producing  areas  are  near  St.  Cloud  and 
Ortonville,  which  are  located  respectively  65  and  179  miles 
northwest  and  west  of  Minneapolis.  Three  kinds  of  granite  are 
quarried  near  St.  Cloud,  viz.,  (i)  a  pinkish  gray  medium-grained 
stone,  used  in  construction  of  the  new  Federal  Building  at  St. 
Paul;  (2)  a  fine-grained  gray  syenite,  and  (3)  a  red  syenite. 

The  price  of  the  St.  Cloud  stone  in  rough  blocks  is  said  to  be 
from  75  cents  to  $1.25  per  cubic  foot. 

The  Ortonville  granite  is  of  dark  red  color  and  medium  to 
coarse  grained,  and  has  been  used  for  structural  and  ornamental 
work  in  both  Minneapolis  and  St.  Paul. 


158  BUILDING  STONES  AND   CLAY-PRODUCTS 

The  Capitol  at  St.  Paul  contains  several  polished  columns  of 
this  stone,  and  the  exterior  of  the  City  Hall  and  County  Court 
House  Building  at  Minneapolis  is  faced  with  red  Ortonville 
granite. 

SOUTHWESTERN  AREA. 
MISSOURI. 

The  igneous  rocks  lie  chiefly  in  the  St.  Francois  Mountains 
area,  and  consist  mainly  of  granite  and  rhyolite. 

The  major  portion  of  the  granite  is  in  an  area  of  about  no 
square  miles,  lying  west  and  southwest  of  Knob  Lick,  but  aside 
from  this  there  are  a  number  of  small  areas  clustered  around 
Fredericktown,  Madison  County. 

The  granite,  which  is  a  quartz-orthoclase-biotite  rock,  with 
subordinate  hornblende,  varies  from  a  light  gray,  through  differ- 
ent shades  of  reddish  pink  to  brownish  red,  but  the  prevailing 
color  is  some  shade  of  red. 

Much  of  it  is  of  porphyritic  texture,  but  still  there  is  much 
variation  from  this.  The  Cornwall  granite  is  very  coarse,  that 
of  Granite ville  a  little  less  so,  while  the  Knob  Lick  is  medium 
grained. 

The  rhyolite  varies  from  many  shades  of  dark  red  and  wine 
color,  to  dark  brown  and  black.  It  is  not  popular  as  a  building 
stone,  for,  although  it  takes  a  good  polish,  it  is  badly  broken  by 
joints. 

Graniteville.  The  largest  and  most  important  quarries  in  the 
state  are  here.  The  stone  is  a  red  granite  of  pleasing  red  color, 
medium  to  coarse  grained,  and  takes  a  good  durable  polish.  It 
is,  therefore,  much  used  for  constructional  and  monumental 
work. 

Blocks  of  large  size  can  be  extracted,  and  columns  16  feet  long 
and  2  feet  6  inches  in  diameter  have  been  obtained. 

Examples.  —  Merchants  Bridge  and  Terminal  Railway,  and  Mercantile  Library, 
St.  Louis,  Mo.;  Thos.  Allen's  Monument,  polished  monolith  of  42  tons  weight, 
Pittsfield,  Mass.;  Post  Offices,  St.  Louis,  Mo.;  and  Cincinnati,  Ohio;  Whitney 
National  Bank,  New  Orleans,  La. ;  columns  on  Flood  Building,  San  Francisco. 

Knob  Lick.  The  granite  of  this  district  is  of  a  gray  to  grayish 
red  color,  and  finer  grained  than  that  of  Graniteville.  Knots 


IGNEOUS  ROCKS  (CHIEFLY  GRANITES)  AND  GNEISSES        159 

are  not  uncommon  in  it  and  may  cause  trouble.     Much  quarry- 
ing for  paving  blocks  was  done  here  in  former  years. 

ARKANSAS. 

Syenite  quarries  have  been  worked  near  Little  Rock.  That 
obtained  on  Fourche  Mountain  is  a  coarsely  crystalline,  dark 
bluish  gray  rock,  which  is  strong  and  durable,  but  may  be 
objected  to  by  some  on  account  of  its  dull  color. 

Example.  —  Pulaski  County  Court  House,  Little  Rock. 

OKLAHOMA. 

The  chief  granite  areas  of  Oklahoma  are  in  the  Wichita  and 
Arbuckle  Mountains. 

Wichita  Mountains.  These  lie  in  southwestern  Oklahoma, 
and  contain  a  number  of  different  kinds  of  igneous  rocks,  but  the 
granite  is  the  most  important. 

It  varies  from  a  dark  red  to  light  pink  and  from  moderately 
coarse  to  finely  granular. 

At  Granite  City,  in  the  northwestern  part  of  the  Wichita 
Mountains,  two  types  of  granite  have  been  quarried.  One  of 
these  is  a  medium-grained,  the  other  a  fine-grained  red  granite. 

In  the  coarser  grained  granite  the  hammered  and  polished  faces 
do  not  show  marked  contrast.  Some  care  has  to  be  used  in 
avoiding  knots  in  quarrying. 

The  finer  grained  granite  takes  a  smoother  polish,  is  a  dark 
brownish  red  on  the  polished  surface,  and  not  so  brittle  as  the 
coarser  grained  stone. 

A  grayish-pink  fine-grained  granite  is  quarried  near  Mountain 
Park,  and  a  gray  fine-grained  one  near  Cold  Springs.  Near  this 
same  locality  a  dark  bluish  gray,  medium-  to  coarse-grained 
anorthosite  has  also  been  worked.  This  rock  is  composed  almost 
entirely  of  a  plagioclase  feldspar  known  as  anorthite.  It  takes 
a  beautiful  bluish  black  polish. 

Arbuckle  Mountains.  These  lie  in  south  central  Oklahoma. 
They  contain  a  coarse-grained  pink  granite  which  has  been 
quarried  and  used  for  building  purposes. 


l6o  BUILDING  STONES  AND   CLAY-PRODUCTS 

TEXAS. 

Granite  occurs  abundantly  in  parts  of  Llano  and  Burnet 
Counties,  some  of  the  stone  being  clean,  but  other  portions 
containing  included  fragments  of  schist. 

The  several  varieties  obtainable  are  as  follows : 

1.  Coarse-grained  pink  variety.     This  is   most   extensively 
quarried  at  Granite  Mountain,  Burnet  County.     It  is  a  biotite 
granite  and  contains  some  pegmatite  dikes. 

Examples.  —  Austin  Capitol,  Galveston  and  Houston  Court  Houses,  and  Gal- 
veston  Sea- wall. 

2.  A  fine-  to  medium-grained  gray  variety.     This  is  quite 
abundant,  and  somewhat  resembles  the  Barre  granite. 

3.  A  fine-  to  medium-grained  pink  variety. 

CORDILLERAN   AREA. 
MONTANA. 

Granite  is  found  in  most  of  the  counties  west  of  and  including 
the  Rocky  Mountains,  but  Lewis  and  Clarke  County  is  the 
largest  producer  in  the  state,  there  being  several  quarries  near 
Helena. 

Next  to  this  region  that  at  Welch's  Spur  near  Butte  is  the 
most  important. 

The  volcanic  ash  deposits  found  near  Dillon  are  usually 
sufficiently  hard  to  be  used  for  building  purposes,  and  many 
buildings  in  Dillon  are  constructed  of  it.  It  is  not  adapted  for 
use  in  large  buildings  and  has  to  be  set  with  a  non-staining 
mortar. 

COLORADO. 

Granites  and  gneisses  are  very  abundant  in  the  whole  moun- 
tainous region  except  in  the  extreme  south.  Many  of  them  are 
suitable  for  building  and  vary  from  dark  gray  to  dark  red. 
Building  granites  are  found  along  the  eastern  border  of  the 
mountains  and  at  Sahda,  Texas  Creek,  Cotopaxi  and  other  points 
within  the  range. 

A  fine-grained  gray  rhyolite  is  quarried  in  large  quantities  at 
Castle  Rock,  south  of  Denver,  and  has  been  extensively  employed 


IGNEOUS  ROCKS  (CHIEFLY  GRANITES)  AND  GNEISSES       l6l 

for  building  in  that  city,  but  more  recently  it  has  been  super- 
seded by  a  similar  rock  of  andesite  nature  from  Del  Norte. 

Although  volcanic  rocks  are  abundant  in  this  state  and  also 
the  other  southwestern  states,  they  are  not  used  to  the  same 
extent  as  in  Mexico,  where  consolidated  tuffs  and  lavas  are 
employed,  not  only  for  constructional  work,  but  also  for  orna- 
mentation. 

CALIFORNIA. 

The  state  contains  extensive  areas  of  granite  and  granite- 
diorite,  but  the  quarrying  industry  of  these  stones  is  compara- 
tively small. 

Rocklin.  This  stone  is  a  light  to  dark-gray  biotite  granite, 
varying  somewhat  in  texture.  The  stone  is  usually  fine  grained 
and  takes  a  good  polish. 

Raymond.  This  is  a  medium  fine-grained  biotite  granite, 
which  sometimes  carries  hornblende.  The  color  is  light  gray. 

Examples.  —  New  Post  Office,  San  Francisco;  three  lower  floors,  Fairmount 
Hotel,  San  Francisco. 

Riverside  County.  Granite  is  abundant  in  this  county  and  has 
been  quarried  for  building  and  ornamental  purposes  at  Corona, 
Riverside  and  Temecula. 

A  small  amount  of  gabbro  is  quarried  at  Penryn. 

OREGON. 

Much  building  stone  is  used  in  Portland,  but  only  a  small  pro- 
portion comes  from  this  vicinity.  The  local  basalt  and  andesite 
have  furnished  material  for  a  few  buildings  but  not  much  now. 

The  black  basalt,  constituting  the  greater  portion  of  the  high- 
land west  of  Portland  has  been  used  extensively  for  foundations. 
Its  dark  color  and  difficulty  in  dressing  are  the  main  objections 
to  its  use. 

The  gray  basalt  of  Rocky  Butte  is  being  used  in  increasing 
quantity. 


CHAPTER   IV. 
SANDSTONES. 

SANDSTONES  are  normally  composed  of  grains  of  quartz  bound 
together  by  some  cementing  substance.  Other  minerals  may  be 
and  often  are  present,  at  least  in  small  quantities.  These  acces- 
sory minerals  include  feldspar,  mica,  iron  oxide,  pyrite  or  even 
tourmaline.  In  rare  cases  feldspar  may  form  the  predominating 
mineral,  and  more  frequently  mica  may  be  so  abundant  as  to 
attract  attention  (Connecticut  brownstone). 

Texture.  Sandstones  range  in  texture  from  very  fine  grained 
ones,  through  those  of  medium  coarseness,  to  extreme  cases  in 
which  the  grains  are  quite  large;  so  by  increasing  coarseness 
they  pass  into  conglomerates.  On  the  other  hand,  by  increasing 
fineness  and  increasing  clayey  matter  they  may  grade  into  shales. 

Hardness.  The  hardness  of  a  rock,  as  already  explained,  de- 
pends on  the  state  of  aggregation  of  the  mineral  grains  and  also 
upon  the  hardness  of  the  grains  themselves.  A  sandstone,  there- 
fore, although  composed  entirely  of  quartz  grains,  might  be  com- 
paratively soft  if  these  grains  were  loosely  cemented. 

The  cementing  material  in  sandstones  may  be  iron  oxide, 
silica,  lime  carbonate,  or  clay.  The  quality  and  character  of 
the  cement  affects  the  strength,  durability,  workability  and  even 
color  of  the  stone.  In  some  sandstones  more  than  one  kind  of 
cementing  material  is  present. 

Silica  cement  is  the  most  durable,  but  if  present  in  too  great 
quantity  makes  the  stone  too  hard  to  work.  The  Berea  sand- 
stone of  Ohio  contains  a  moderate  amount  of  siliceous  cement, 
while  the  Potsdam  sandstone  of  New  York  is  strongly  cemented 
with  the  same  material. 

Iron  oxide  may  also  act  as  a  strong  binder  of  the  sandstone 
grains,  but  does  so  to  a  less  degree  than  silica,  and  at  the  same 
time  it  imparts  color  to  the  stone. 

162 


SANDSTONES  163 

Calcium  carbonate,  though  giving  a  fairly  strong  cement,  is  an 
undesirable  one,  for  the  reason  that  it  is  not  only  soft  but  readily 
dissolves  in  carbonated  waters.  It  rarely  produces  any  notice- 
able discoloration.  It  can  be  detected  usually  by  the  efferves- 
cence when  a  drop  of  cold  dilute  muriatic  acid  is  put  upon  the 
stone.  Small  amounts  do  no  special  harm. 

Clay  as  a  cement  possesses  both  advantages  and  disadvan- 
tages. It  is  not  as  strong  as  the  others,  and  moreover  serves  to 
attract  moisture  to  the  stone;  hence  an  excess  of  clay  might  render 
the  sandstone  liable  to  injury  from  frost.  A  small  amount  is  an 
advantage,  as  it  softens  the  stone  somewhat  and  facilitates 
dressing.  If  present,  the  clay  should  be  uniformly  distributed, 
for  its  occurrence  in  thin  seams  may  cause  the  rock  to  split  or 
flake  off  along  these. 

Color.  This  may  be  due  to  iron  compounds,  clay  or  car- 
bonaceous matter. 

Limonite  (hydrous  iron  oxide)  colors  a  sandstone  various 
shades  of  buff,  yellow  and  yellow-brown.  Hematite  (iron  oxide) 
may  give  red  or  red-brown  tints.  But  if  the  iron  is  unevenly 
distributed  a  blotchy  appearance  is  produced. 

A  faint  bluish  or  greenish  tint  is  possibly  due  to  iron  sulphide, 
iron  carbonate,  or  more  rarely  iron  silicate  being  present  in  a  very 
finely  divided  condition. 

Clay  will  often  impart  a  grayish  color  to  a  sandstone,  and  a,t 
the  same  time  a  somewhat  dull  or  earthy  appearance.  Car- 
bonaceous matter  may  also  cause  gray  or  black  coloration. 

Absorption.  Sandstones  show  a  wide  range  of  absorption. 
Hard,  dense  ones,  like  quartzites,  will  absorb  under  i  per  cent  of 
their  weight  of  water.  Many  absorb  2  to  3  per  cent  and  very 
porous  ones  take  up  as  much  as  10  or  1 1  per  cent. 

Crushing  Strength.  The  average  of  many  tests  shows  a  range 
of  from  9000  to  12,000  pounds  per  square  inch.  Some  well- 
known  ones  run  as  low  as  5000  pounds  per  square  inch,  while 
hard  sandstones  and  quartzites  not  infrequently  show  a  crushing 
strength  of  15,000  or  even  more  pounds. 

The  following  table  contains  some  tests  of  sandstone  from 
different  localities. 


164 


BUILDING  STONES  AND   CLAY-PRODUCTS 


TESTS  OF    SANDSTONE. 


Locality. 

Crushing  Strength. 

Transverse 
strength, 
modulus 
of  rupture. 

Ab- 
sorp- 
tion per 
cent. 

Spec, 
grav. 

Posi- 
tion. 

Lbs.  per 

sq.  in. 

Presque  Isle,  Wis 

Bed 
Edge 
Bed 
Edge 
Bed 
Edge 
Bed 
Edge 

6,244 
4,747 
4,549 
4,090 
2,502 
2,942 
5,498 
1,658 
12,580     • 

12,210 

Presque  Isle,  Wis  

Houghton,  Wis.  . 

574-6 

8.89 
15.22 

Houghton,  Wis  

Dunville,  Wis  

2.582 
2.649 

2-35 
2-49 

2  .604 
2.16 

2.66 

Dunville,  Wis 

Port  Wing,  Wis. 

2073 

10.33 

aloS 

5.00 
4.00 

Port  Wing,  Wis.                    .    . 

Portland,  Conn  

E.  Longmeadow,  Mass  
Potsdam,  N.  Y. 

Marquette,  Mich. 

3,800 

14,753 
l6,03I 

n,547 
11,213 

5,9H 
4,869 

6,309 
8,880 
8,500 
19,022 
i  5,750 
(  3,270 

Waltonville,  Pa  
Medina,  N.  Y  
Kettle  River,  Minn. 

Berea,  O. 

Warrensburg,  Mo  
Warrensburg,  Mo  
Flagstaff,  Ariz  

Bed 
Edge 

777-97 

7.64 

Y.76' 

3-025 

3-9 

2.649 

2.346 
2.558 
2.34 

Colusa   Cal 

Columbus,  Mont. 

Warsaw,  N.  Y. 

Tenino,  Wash  

The  following  analyses  are  given  for  those  who  may  desire 
them,  to  show  the  variation  in  composition  of  several  sandstones 
used  for  building. 


I. 

ii. 

in. 

IV. 

V. 

VI. 

Silica  (S02)  
Alumina  (A12O3)  
Ferric  oxide  (Fe2O3)  .  . 
Lime  (CaO)  
^Magnesia  (MgO) 

70.11 
13-49 
4-85 
2-39 

I    44. 

84.40 

7-49 
3-87 
0.74 

2  II 

89-33 
6.05  1 
1.41  \ 
trace 
trace 

76.53 
ii-37 
9-561 

O   AI 

76.50 

i  H-75 
1    6.35 

90.34 

4-35 
1.09 

o-95 

O    17 

Potash  (K20)  j 
Soda  (Na2O)    > 

7    37 

C   0.24 
<    o  56 

2.12 

o  50 

I.30 

o.  19 

Water  (H2O)  ) 

I.: 

2.00 

0.61 

1  As  carbonates. 


I.  Portland,  Conn.;    II.   Berea,  Ohio;    III.   Port  Wing,  Wis.;    IV.   Warrens- 
burg, Mo.;  V.   Warsaw,  N.  Y.;  VI.   Hummelstown,  Pa. 


SANDSTONES  165 

Weathering  Qualities.  Sandstones,  as  a  rule,  show  good  dura- 
bility. Some  of  the  softer  ones  may  disintegrate  under  frost 
action.  Those  with  clay  seams  are  liable  to  split  with  continued 
freezing.  Mica  scales,  if  abundant  along  the  bedding  planes,  are 
also  likely  to  cause  trouble,  and  this  is  aggravated  if  the  stone 
is  set  on  edge  instead  of  on  bed.  A  striking  example  of  this  is 
the  Connecticut  brownstone  so  extensively  used  in  former  years 
for  fronts  in  many  of  the  eastern  cities.  In  order  to  get  a  smooth 
surface  it  was  rubbed  parallel  with  the  bedding,  and  the  stone 
set  in  the  building  on  edge.  The  result  is  that  hundreds  of 
buildings  put  up  more  than 'fifteen  or  twenty  years  ago  are  scaling 
badly,  and  in  many  cases  the  entire  front  has  been  redressed. 

Sandstones  sometimes  change  from  gray  to  buff  or  brown  on 
exposure  to  the  weather  due  to  the  oxidation  of  the  iron,  but  this 
does  not  necessarily  indicate  deterioration  of  the  stone. 

Fire  Resistance.  Sandstones  are  perhaps  as  little  affected  by 
a  heat  of  1500°  F.  as  any  building  stones,  but  are  likely  to  spall 
and  crack  when  exposed  to  the  combined  effects  of  fire  and  water. 
Some  show  a  tendency  to  split  along  the  bedding  planes. 

VARIETIES  OF  SANDSTONE. 

The  following  variety  names  are  based  on  difference  in  color, 
mineral  composition  and  texture. 

Arkose.  A  sandstone  composed  chiefly  of  feldspar  grains. 
Some  is  quarried  in  New  Jersey. 

Bluestone.  The  name  belongs  properly  perhaps  to  a  flagstone 
much  quarried  in  eastern  New  York.  It  is  also  used  for  bluish 
gray  sandstones  quarried  at  other  points,  as,  for  example,  the 
Warsaw  bluestone  of  western  New  York. 

Brownstone.  A  term  formerly  applied  to  sandstones  of  brown 
color,  obtained  from  the  Triassic  formation  of  the  Connecticut 
Valley  of  Connecticut  and  Massachusetts,  and  in  other  eastern 
states,  but  since  stones  of  other  colors  are  found  in  the  same 
formation,  the  term  has  come  to  have  a  geographic  meaning  and 
no  longer  refers  to  any  specific  physical  character. 

Calcareous  Sandstone.  One  in  which  carbonate  of  lime  forms 
the  cementing  material. 


1 66  BUILDING   STONES  AND   CLAY-PRODUCTS 

Ferruginous  Sandstone.  One  containing  considerable  iron 
oxide  in  the  cement. 

Flagstone.  A  thinly  bedded,  argillaceous  sandstone  used 
chiefly  for  paving  or  flagging  purposes. 

Freestone.  A  sandstone  which  splits  freely  and  dresses 
easily. 

Graywacke.  A  hard  sandstone  of  compact  character,  com- 
posed of  grains  of  quartz,  feldspar,  slate  and  perhaps  other 
minerals,  with  a  clayey  cement. 

Quartzite.  A  very  hard,  usually  very  dense  sandstone,  which 
owes  its  hardness  to  pressure,  or  more  commonly  deposition  of 
silica  around  the  grains. 

Distribution  of  Sandstones  and  Quartzites.  Sandstones  and 
quartzites  are  widely  distributed  in  the  United  States;  indeed, 
so  much  so  that  there  are  numerous  small  quarries  opened  up 
in  many  states  to  supply  a  local  demand. 

In  a  few  cases,  certain  areas  have  been  worked  on  a  large  scale 
to  supply  a  wide  extent  of  territory.  This  is  true  of  the  Con- 
necticut brownstone,  so  much  worked  in  former  years,  and  of  the 
Berea  sandstone  of  Ohio,  which  is  extensively  used  now  in  the 
eastern  and  central,  and,  to  not  a  small  extent,  in  the  western 
states. 

In  view  of  this  wide  distribution  of  sandstone,  it  becomes  some- 
what difficult  to  pick  out  a  few  prominent  areas. 

NEW  ENGLAND  STATES. 

Sandstones  are  of  little  importance  in  most  parts  of  New 
England. 

The  best  known  is  that  of  the  Triassic  formation  of  Connecti- 
cut and  Massachusetts,  which  has  been  widely  used  in  former 
years.  This  is  a  rather  fine-grained  sandstone,  usually  of  reddish 
brown  color,  moderate  density,  and  not  extra  hard.  It  lies  in 
horizontal  beds  which  vary  from  a  few  inches  to  twenty  feet  in 
thickness  (Merrill).  On  account  of  the  large  amount  of  quarry 
water  which  it  contains  it  cannot  be  quarried  in  freezing  weather; 
indeed,  Merrill  states  that  a  temperature  of  22°  F.  is  sufficient  to 
freeze  and  burst  blocks  of  the  freshly  quarried  material;  but  a 


SANDSTONES  167 

week  or  ten  days  of  good  drying  weather  is  considered  enough  to 
protect  the  stone  against  frost. 

The  fact  that  the  stone  splits  under  frost  action  when  set  on 
edge  instead  of  on  bed  has  somewhat  injured  its  reputation. 

A  brick-red  variety  of  fine  uniform  grain  is  quarried  at  Kibbe, 
and  East  Longmeadow,  Mass. 

The  Connecticut  brownstone  has  been  extensively  used  in  the 
eastern  cities  for  constructional  work,  and  especially  as  veneer 
blocks  over  brick  for  the  fronts  of  buildings.  It  has  also  been 
much  employed  in  former  years  for  headstones  in  cemeteries. 
The  Kibbe  rock  has  found  similar  applications. 

Examples.  —  Academy  of  Design,  Brooklyn,  N.  Y.;  Wesleyan  University 
Buildings,  Middletown,  Conn.;  Holy  Trinity  Episcopal  Church,  New  York  City; 
Court  House  and  Post  Office,  Rochester,  N.  Y. ;  lower  stories  of  Waldorf-Astoria 
Hotel,  New  York  City;  Marshall-Field  Building,  Chicago,  111.  (Kibbe  sandstone 
above  basement);  Trinity  Church,  Boston,  Mass.;  Library  and  Stock  Building, 
Princeton  University,  Princeton,  N.  J. ;  numerous  private  residences  in  Boston, 
New  York,  Philadelphia  and  other  eastern  cities. 


EASTERN  ATLANTIC  STATES. 

These  contain  an  abundance  of  sandstone  suitable  for  building 
purposes. 

They  may  be  briefly  summarized  as  follows: 

NEW  YORK. 

Medina  Sandstone.  A  moderately  fine-grained  sandstone  of 
light  gray  (called  white)  or  red  color  and  quarried  chiefly  be- 
tween Rochester  and  Lockport.  The  red  is  used  chiefly  for 
building  purposes,  and  has  a  bright  color.  The  gray  may  be 
used  with  it,  but  its  main  use  is  for  paving  blocks. 

Both  types  are  stones  of  good  durability  and  low  absorption. 

Potsdam  Sandstone.  This  is  essentially  a  quartzite,  usually 
very  hard,  dense,  moderately  fine-grained,  and  of  red  or  reddish 
brown  color.  It  is  perhaps  less  used  now  than  formerly.  Its 
main  occurrence  is  in  northwestern  New  York,  but  it  is  also 
found  in  the  east  along  Lake  Champlain. 

Examples.  —  Many  buildings  in  Potsdam,  N.  Y.;  All  Saints  Cathedral  in  Al- 
bany, N.Y.;  parts  of  the  Dominion  Houses  of  Parliament,  Ottawa,  Canada. 


1 68  BUILDING  STONES  AND   CLAY-PRODUCTS 

Warsaw  Bluestone.  A  fine-grained  bluish  gray  sandstone  of 
earthy  appearance,  much  used  for  constructional  work,  but 
especially  for  trimmings  in  many  of  the  eastern  cities. 

Examples.  —  University  Avenue  M.  E.  Church,  Syracuse,  N.  Y.;  Genesee 
Street  Baptist  Church,  Rochester,  N.  Y. 

Hudson  River  Bluestone.  The  typical  bluestone  is  a  fine- 
grained, compact,  tough  sandstone,  of  blue-gray  color,  which 
breaks  up  readily  into  slabs  a  few  inches  thick,  and  sometimes 
of  large  size.  On  this  account  it  has  been  extensively  used  for 
flagging,  curbs,  sills,  steps,  etc.  It  is  quarried  chiefly  in  Albany, 
Green  and  Ulster  Counties.  Some  slabs  of  large  size  have  been 
extracted. 

NEW  JERSEY. 

Sandstones  occur  in  many  parts  of  the  state.  Lewis 
enumerates : 

1.  Brown  sandstone,  or  brownstone,  and  also  gray  and  white 
sandstones  abundant  in  Triassic  belt  across  central  part  of  state. 
The  white  and  gray  occur  at  many  points  from  the  Delaware  to 
the  Hudson  and  are  much  used.     They  consist  of  quartz  or 
quartz  and  feldspar. 

2.  Conglomerates  and  sandstones  of  Kittatinny  Mountain 
region,  southwest  of  Greenwood  Lake. 

3.  White   to  gray   sandstone   or   quartzite   in  northwestern 
counties. 

4.  Reddish,  purplish  and  bluish  gray  argillites  around  Prince- 
ton, Lawrence ville  and  Byram. 

5.  Flagstones  of   Hunterdon,  Warren  and   Sussex  counties. 
Of  these  the  first  has  been  most  important,  but  the  demand  is 
less  than  formerly.     Much  of  that  cut  below  water  level  hardens 
as  the  stone  dries  out.     The  localities  of  production  include 
Chester,   Ridgefield,  Watchung,   Martinsville,   Princeton,   Wil- 
burtha,  Stockton. 

Brownstone  is  also  quarried  at  several  points,  including  Little 
Falls,  Paterson,  Belleville,  etc. 

Examples.  —  Trinity  Church,  N.  Y.;  Queen's  Building,  Rutgers  College,  New 
Brunswick,  N.  J. ;  Old  Court  House,  Newark,  N.  J. 


SANDSTONES  169 

PENNSYLVANIA. 

The  Triassic  sandstone  formation  crosses  Pennsylvania  from 
New  Jersey  to  Maryland,  the  chief  quarries  being  at  Hummels- 
town,  Dauphin  County. 

The  rock  obtained  there  is  evenly  bedded,  fine  grained  and 
takes  a  smooth  finish.  Two  shades  are  quarried,  the  most 
abundant  being  of  a  dark  reddish  brown  color,  resembling  the 
sandstone  from  East  Longmeadow,  Mass. ;  the  other  is  a  purplish 
brown.  The  stone  is  practically  free  from  mica  and  has  not 
been  observed  to  scale  off.  The  Hummelstown  stone  has  been 
widely  used. 

Examples.  —  The  Market  and  Fulton  National  Bank,  New  York  City;  Salem 
Lutheran  Church,  Lebanon,  Pa.;  High  School,  Altoona,  Pa.;  Presbyterian  Church, 
Indiana,  Pa.;  Emory  Methodist  Episcopal  Church,  Pittsburg,  Pa.;  Union  Station, 
Indianapolis,  Ind. 

In  western  Pennsylvania,  there  are  numerous  sandstones  in 
the  Coal  Measures  formations,  but  they  are  little  used  except 
for  local  purposes. 

Near  Pittsburg  there  are  many  quarries  which  produce  small 
quantities  of  stone,  and  not  a  few  of  these  are  said  to  weather 
unevenly,  owing  to  presence  of  calcareous  matter,  and  are  sensi- 
tive to  frost. 

The  Wyoming  County  stone,  known  to  the  trade  as  Wyoming 
Valley  stone,  is  said  to  resemble  the  New  York  bluestone. 

MARYLAND. 

There  is  only  one  sandstone  within  the  state  which  has  at- 
tained any  reputation  as  a  building  stone  and  that  is  the  so-called 
Triassic  or  "Seneca  Red."  There  are  other  sandstone  areas  in 
other  parts  of  the  state,  but  they  are  quarried  only  for  local  use. 
The  Seneca  red  stone  is  from  the  same  formation  that  supplies 
the  brownstone  of  Portland,  Conn.,  and  that  of  Hummels- 
town, Pa.  The  prominent  quarries  are  situated  near  the  mouth 
of  Seneca  Creek,  Montgomery  County.  The  stone  occurs  in 
workable  beds  varying  in  thickness  from  18  inches  to  6  or  7  feet, 
and  these  are  separated  from  each  other  by  bands  of  inferior 
material  of  different  color  and  texture.  The  sandstone  beds, 


170  BUILDING   STONES  AND   CLAY-PRODUCTS 

themselves,  differ  very  much  not  only  in  color  but  also  in  hard- 
ness and  texture. 

The  texture  of  the  stone  placed  on  the  market  is  fine  grained 
and  uniform,  not  at  all  shaly,  and  shows  little  or  no  tendency  to 
scale  when  exposed  to  the  weather. 

It  is  said  to  be  soft  enough  to  carve  and  chisel  readily  when 
quarried,  but  after  exposure  becomes  hard  enough  to  turn  the 
edge  of  well-tempered  tools.  Its  color  varies  from  an  even,  light 
reddish  brown  or  cinnamon  to  a  chocolate  or  deep  purple  brown. 
It  is  brighter  when  first  quarried. 

Matthews  gives  several  instances  of  the  use  of  this  stone 
which  show  its  durability.  The  Smithsonian  Institute,  erected 
between  1848-1854,  shows  few  defects  from  weathering  alone. 

VIRGINIA. 

This  state  contains  a  number  of  sandstone  formations,  but 
none  are  worked  for  any  except  local  use. 

WEST  VIRGINIA. 

There  are  a  number  of  sandstones  in  this  state  but  they  are 
mainly  of  local  value. 

ALABAMA. 

In  the  Coal  Measures  area  of  the  state,  sandstones  have  been 
worked  at  Jasper  and  Cullman,  and  at  Tuscaloosa. 

The  locks  on  the  Warrior  River  at  the  last-named  place  are 
constructed  of  this  stone. 

The  Hartselle  (Lower  Carboniferous)  sandstone  is  quarried 
near  Cherokee,  Colbert  County,  and  has  been  used  for  the  locks 
at  the  Colbert  Shoals  on  the  Tennessee  River. 

The  Weisner  sandstone  has  furnished  the  material  for  many 
buildings  around  Anniston. 

CENTRAL  STATES. 

OHIO. 

There  are  several  sandstone-producing  formations  in  Ohio,  but 
by  far  the  most  important  is  that  known  as  the  Berea  sandstone 
or  Berea  grit. 


PLATE  XXX.— U.  S.  Post  Office,  Toledo,  Ohio,  constructed  of  Gay  "Canyon" 
Berea  sandstone.     (Photo  loaned  by  Cleveland  Stone  Co.) 

171 


SANDSTONES  173 

This  stone,  which  is  widely  used  for  building  purposes,  is  of 
fine,  even-grained  texture,  very  light  buff -gray  color  and  evenly 
bedded. 

It  is  moderately  porous  and  not  extra  hard,  so  that  it  can  be 
easily  carved  and  cut. 

In  the  best  grades  the  sulphide  of  iron  (pyrite)  is  finely  divided 
and  evenly  distributed,  and  on  exposure  to  the  air  the  stone 
turns  yellowish.  This,  however,  does  not  seem  to  affect  the 
durability  or  appearance  of  the  stone.  If  the  pyrite  is  unevenly 
distributed  the  stone  has  a  blotched  appearance,  and  such  pieces 
are  undesirable. 

The  principal  quarries  are  located  in  the  town  of  Amherst, 
Berea  and  East  Cleveland. 

Examples.  —  Almost  every  large  city  contains  structures  of  Berea  sandstone. 
Among  these  maybe  mentioned:  Soldiers  and  Sailors  Memorial  Hall,  Pittsburg,  Pa.; 
Goldwin  Smith  Hall,  Cornell  University,  Ithaca,  N.  Y.;  Wayne  County  Court 
House,  Detroit,  Mich.;  City  Hall,  St.  Louis,  Mo.;  U.  S.  Post  Office  and  Court 
House,  Minneapolis,  Minn. 

A  stone  known  as  the  Euclid  bluestone  is  obtained  in  Euclid 
and  Newburgh  in  Cuyahoga  County.  It  differs  from  the  Berea 
in  being  finer  grained  and  of  a  blue-gray  color.  Like  the  Berea 
it  contains  much  pyrite,  but  does  not  weather  uniformly,  becom- 
ing blotchy.  Its  chief  use  is  for  bridge  work,  foundations  and 
nagging. 

INDIANA. 

Sandstones  of  good  quality  are  known  in  the  Coal  Measures 
formations  of  western  Indiana,  but  the  production  is  exceedingly 
small.  Three  may  be  mentioned. 

The  Mansfield  sandstone  lies  at  the  base  of  the  Coal  Measures 
and  outcrops  in  a  band  2  to  20  miles  wide  and  175  miles  long, 
extending  southeast  from  the  northern  part  of  Warren  County. 
It  consists  of  quartz  grains  with  iron  oxide  cement,  the  color 
sometimes  being  dark  brown,  but  more  often  buff  or  gray. 
The  former  (brown)  is  extensively  used  for  trimming,  while  the 
latter  is  quarried  for  local  use. 

The  Knobstone  sandstone  is  a  fine-grained,  light  blue  or  drab- 
colored  rock,  well  adapted  to  smooth  finish  or  fine  carving.  It 


174  BUILDING  STONES  AND   CLAY-PRODUCTS 

is  quarried  somewhat  extensively  in  Fountain  County,  but  is  not 
very  durable  unless  carefully  selected  and  set. 

The  Coal  Measures  sandstone  is  finer  grained  than  the  Mans- 
field, buff,  blue  or  gray  in  color,  and  very  durable.  It  is  said  to 
weather  to  a  rusty  yellow  not  very  pleasing  to  the  eye.  This 
rock  has  been  quarried  in  some  quantity  at  Worthy,  Vermillion 
County,  and  Cannelton,  Perry  County. 

ILLINOIS. 

Sandstones   are   quarried  in   Henry,    St.    Clair   and   Carroll 

counties. 

MICHIGAN. 

The  Potsdam  formation  outcropping  on  the  Upper  Peninsula 
is  the  most  important  source  of  sandstone  in  this  state.  That 
quarried  at  Marquette  is  a  moderately  fine-grained  sandstone, 
of  brownish  red  color,  often  spotted  with  gray.  The  gray  spots 
as  well  as  the  occasional  presence  of  clay  holes  and  flint  pebbles 
make  a  careful  selection  of  the  stone  necessary. 

At  Jacobsville,  on  Keweenaw  Bay,  the  same  formation  sup- 
plies a  stone  of  uniform,  bright  red  color,  even  structure  and 
texture,  which  has  been  much  used  for  general  building  purposes 
and  trimming.  It  is  very  porous,  but  seems  to  stand  the  weather 
well.  The  basement  of  the  Cornell  University  Library  is  con- 
structed of  it,  and  after  twenty  years  of  exposure  to  a  severe 
climate  shows  no  ill  effects. 

Sandstones  for  local  use  are  quarried  in  the  Coal  Measures 
formation  of  Southern  Michigan. 

WISCONSIN. 

One  of  the  most  widely  distributed  sandstones  and  one  which 
has  furnished  the  greatest  variety  in  color  and  texture  is  the  sand- 
stone of  the  Potsdam  and  St.  Peter's  formations. 

The  Potsdam  sandstone  forms  a  curved  belt  extending  from 
the  northeastern  part  of  the  state  near  Menominee,  southwest- 
ward  and  then  northwestward  to  the  St.  Croix  River. 

In  this  belt  the  stone  is  quarried,  among  other  points,  at  Dunn- 
ville.  The  sandstone  in  general  is  a  very  light  buff,  although 
some  of  the  beds  are  more  of  a  gray  or  bluish  white.  The  texture 


SANDSTONES  175 

varies  from  fine  to  coarse,  and  when  first  quarried  the  stone  cuts 
easily  and  carves  well.  This  stone  is  a  good  example  of  one, 
containing  a  very  high  amount  of  quarry  water. 

Examples.  —  Mabel  Taintor  Memorial  Building,  Menominee,  Wis. ;  Masonic 
Temple,  St.  Paul,  Minn.;  Pierce  County  Court  House,  Ellsworth,  Wis. 

A  second,  but  narrow,  belt  skirts  the  south  shore  of  Lake 
Superior. 

The  latter  area  is  known  as  the  Lake  Superior  sandstone,  while 
the  large  belt  is  known  as  the  southern  Potsdam  sandstone. 

The  northern  belt  supplies  a  brownstone  and  is  quarried 
around  Bayfield  and  Washburn. 

The  stone  is  of  a  brown-red  color,  fine  grained,  not  easily 
injured  by  frost,  and  of  good  fire  resistance.  No  trouble  is 
experienced  in  getting  rocks  of  large  dimensions.  Some  beds 
show  clay  holes,  others  whitish  discolorations,  and  still  others 
are  of  pebbly  character,  but  these  can  be  avoided  in  quarrying. 

Several  possible  causes  have,  perhaps,  reacted  against  the  in- 
dustry, viz.,  fashion,  improper  use  of  brownstone,  and  shipment 
of  inferior  stock. 

The  stone  must  not  be  quarried  in  freezing  weather. 

Examples  of  Lake  Superior  brownstone:  Court  House,  Milwaukee,  Wis.; 
Central  High  School,  Duluth,  Minn.;  Court  House,  Washburn,  Wis.;  Law  Build- 
ing, Winnipeg,  Man.;  Walnut  Street  Opera  House,  Cincinnati,  Ohio;  Tribune 
Office  Building,  Chicago,  111. 

The  St.  Peter's  formation  forms  a  narrow  strip,  extending 
from  the  Menominee  River,  in  a  southerly  and  westerly  direction. 
It  is  white,  brown,  red  or  yellow;  medium  and  coarse  grained, 

and  not  always  hard. 

MINNESOTA. 

Large  sandstone  quarries  are  in  operation  at  Sandstone  on  the 
Kettle  River.  The  rock  is  a  fine-grained,  light  pink  stone,  said 
to  be  hard  and  durable.  Only  about  20  feet  of  the  80  foot  face 
are  selected  for  choice  building  stone,  and  much  of  the  upper 
courses  is  used  for  paving  blocks  and  heavy  masonry.  Blocks 
5  to  10  feet  long  can  be  easily  obtained. 

The  approximate  prices  of  this  stone  are:  Rock-faced  dimen- 
sion stone,  $i  to  $1.25  per  cubic  foot,  f.o.b.;  sandstone,  two  sides, 
50  cents  per  cubic  foot;  paving  blocks,  $1.50  per  cubic  yard. 


176  BUILDING  STONES  AND   CLAY-PRODUCTS 

This  stone  is  extensively  used  for  building  purposes  in  the 
Mississippi  Valley  states  and  makes  a  good  structural  material. 

Examples.  —  Library  Building,  University  of  Illinois;  United  Presbyterian 
Church  (interior),  Worcester,  Mass.;  Spokane  Club  Building,  Spokane,  Wash.; 
Des  Moines,  la.,  Public  Library. 

A  good  quality  of  quartzite  is  extensively  quarried  at  New 
Ulm  and  makes  a  satisfactory  building  material. 

MISSOURI. 

The  most  important  sandstone  quarries  in  the  state  are  located 
at  Warrensburg  and  Miami.  The  formation  supplies  large 
blocks  of  sandstone  of  either  blue  or  white  color.  Some  of  the 
stone  is  reedy  and  hence  care  is  required  in  selecting  it.  The 
stone  hardens  on  exposure  to  the  atmosphere. 

ARKANSAS. 

This  state  is  not  important  as  a  producer  of  sandstone  but  the 
northern  part  of  the  state,  according  to  Branner  (Stone,  October, 
1889),  is  said  to  contain  a  great  quantity  of  cream-colored  cal- 
ciferous  sandstone  which,  on  account  of  its  color,  firmness  and 
massiveness,  makes  it  desirable  for  architectural  purposes. 

Gray  sandstones  come  from  coal  regions  of  the  state  but  are 
not  used  to  any  great  extent. 

WESTERN  STATES. 

MONTANA. 

Sandstone  is  quarried  in  between  twelve  and  fifteen  counties 
in  the  state,  but  the  quarries  near  Columbus,  Yellowstone 
County,  are  by  far  the  most  important.  This  locality  supplies 
a  sandstone  of  bluish  color,  fine  grain,  and  unusually  even 
texture,  the  latter  reminding  one  somewhat  of  the  Berea  stone. 
The  stone  at  times  shows  a  cross-bedded  structure. 

Example.  —  Capitol  at  Helena,  Mont. 

COLORADO. 

A  number  of  good  sandstones  are  found  in  this  state,  but  owing 
to  small  demand  and  poor  transportation  facilities  they  are 
little  used.  The  most  important  ones  are  the  so-called  red  beds 
which  are  found  at  a  number  of  points  in  the  state.  A  belt 


SANDSTONES  177 

of  these  extends  along  the  foothills  of  the  mountains,  passing 
through  Manitou  and  Boulder.  This  formation  supplies  a 
variety  of  stone,  including  a  bright  red  stone  which  is  often  used 
for  structural  purposes  and  white,  hard  sandstone  and  also  some 
softer  sandstone.  Many  of  these  are  not  very  durable. 

The  first  of  these  is  known  as  the  Manitou  stone  because  it  is 
quarried  largely  near  that  place.  This  stone  works  very  easily 
and  has  been  much  used  in  public  and  private  buildings  in 
Denver.  The  harder  type  of  sandstone,  from  the  Red  Beds, 
which  is  said  by  Merrill  to  be  used  for  flagging  and  foundation, 
has  been  quarried  at  Bellvue,  Stout  and  Arkins  in  Larimer 
County;  at  Lyons,  Boulder  and  at  other  points  in  the  foothills. 
This  stone  is  a  deep  red  color.  A  light-colored  sandstone,  some- 
what resembling  the  Berea  sandstone,  has  been  quarried  near 
Canyon  City  and  was  used  in  the  construction  of  the  Court 

House  at  Denver. 

WASHINGTON. 

Sandstones  are  found  at  a  number  of  points  in  the  state,  but 
the  chief  deposits  occur  on  the  western  side  of  the  Cascade 
Mountains. 

The  Tenino  stone  is  a  fine-grained,  dark-colored  sandstone, 
with  some  mica,  and  hardens  considerably  after  being  quarried. 

Examples.  —  High  School  Building,  Seattle;  Trinity  Church,  Seattle;  Calvary 
Presbyterian  Church,  San  Francisco,  Cal. 

A  blue-gray  Carboniferous  sandstone  has  been  quarried  near 
Bellingham.  It  is  fine  grained  and  somewhat  harder  than  the 
Tenino  sandstone. 

Examples.  —  U.  S.  Custom  House,  Port  Townsend;  U.  S.  Custom  House,  Port- 
land, Ore.;  Thurston  County  Court  House,  Olympia. 

CALIFORNIA. 

The  most  important  sandstone-producing  district  of  Cali- 
fornia is  in  Colusa  County. 

Examples.  —  Kohl  Building,  San  Francisco;  St.  Francis  Hotel,  San  Francisco; 
Jas.  L.  Flood  Building,  San  Francisco. 

The  Leland  Stanford  Buildings  are  constructed  of  sandstone 
from  south  of  San  Jose,  Santa  Clara  County.  It  is  buff  and 
light  gray. 


CHAPTER   V. 
LIMESTONES   AND   MARBLES. 

LIMESTONES  AND  DOLOMITES. 

UNDER  the  name  of  limestone  there  is  included  a  group  of 
stratified  rocks  which  consists  essentially  of  calcium  carbonate. 

They  are  sometimes  quite  impure,  the  common  impurities, 
any  or  all  of  which  may  be  present  in  varying  amounts,  being 
iron  oxide,  silica,  clay  and  carbonaceous  matter.  Magnesia  is 
likewise  rarely  absent,  and  with  an  increase  of  it  the  stone  passes 
into  a  typical  dolomite,  which  chemically  consists  of  54.35  per 
cent  lime  carbonate  and  45.65  per  cent  magnesium  carbonate. 

With  an  increase  in  silica  the  rock  passes  into  a  calcareous 
sandstone;  with  an  increase  of  clay,  into  a  calcareous  shale. 

A  limestone  which  has  been  rendered  crystalline  by  meta- 
morphism  is  termed  a  marble,  and  this  type  is  treated  under  a 
separate  heading.  It  may  also  include  some  limestones  of 
crystalline  texture,  which  have  not  a  metamorphic  origin. 
These  may  be  regarded  as  marbles  in  a  commercial  sense,  but  are 
not  strictly  so  geologically. 

Color.  Limestones  show  a  great  range  of  color,  the  most 
common  shades  being  blue,  gray,  white  and  black,  but  other 
colors,  due  chiefly  to  iron  compounds,  may  occur,  although  these 
more  brilliant  and  beautiful  colors  are  seen  chiefly  in  the  marbles. 

Hardness.  Both  calcite  and  dolomite  are  soft  minerals,  but 
the  rocks  of  which  they  form  the  main  constituent  are  often  very 
hard.  Limestones,  however,  as  a  class,  show  a  great  variation  in 
their  hardness.  Some  are  so  soft  as  to  be  readily  cut  with  a  saw, 
as,  for  example,  coral  rock,  the  Caen  stone  of  France,  and  others. 
The  Bedford  limestone  of  Indiana  is  moderately  hard,  while  the 
Shenandoah  limestone  of  the  southern  states  is  a  very  firm  rock. 

Texture.  Most  limestones  are  fine  grained,  indeed,  so  fine  that 
the  individual  grains  are  not  noticeable  with  the  naked  eye. 

178 


Plate  XXXI,  Fig.  i.  —  Limestone  showing  dark  flint  nodules. 


PLATE  XXXI,  Fig.  2.  —  Tremolite  in  dolomitic  marble. 


179 


LIMESTONES  AND   MARBLES  l8l 

Some  are  moderately  fine  grained,  as  the  oolitic  limestones,  while 
others  are  coarse  grained,  due  largely  to  the  presence  of  numerous 
fossils.  The  Coquina,  found  near  St.  Augustine,  Fla.,  is  to 
be  classed  with  the  last  named. 

Absorption.  The  majority  of  the  harder  limestones  have  a 
very  low  absorption,  usually  under  two  per  cent.  Some  widely 
used  ones  may  run  much  higher.  Thus  the  Bedford,  Ind., 
limestone  shows  4  or  5  per  cent;  the  French  Caen  stone,  10  to 
12  per  cent;  the  Roman  travertine  still  more. 

Weathering  qualities.  Both  limestones  and  dolomites,  if  dense 
and  massive,  are  moderately  durable,  though  not  to  be  compared 
with  good  sandstones  or  granites. 

Limestones  weather  primarily  by  solution ;  that  is  to  say,  rain 
or  surface  water  may  slowly  attack  the  rock,  but  the  solution  of 
the  surface  may  go  on  very  unevenly.  If  certain  portions  are 
silicified,  such  as  fossils  which  have  been  replaced  by  silica,  or 
if  quartz  veins  are  present  in  the  rock,  these  resist  the  solvent 
action  of  surface  waters  more  than  the  surrounding  calcareous 
parts  of  the  rock  and  are  left  standing  out  in  relief,  giving  the 
stone  a  rough  appearance. 

Dolomites  do  not  weather  so  readily  by  solution,  but  dis- 
integrate, breaking  off  a  grain  at  a  time.  This  is  specially 
noticeable  in  some  coarse-grained  ones,  which  have  been  exposed 
to  the  weather  for  from  forty  to  fifty  years. 

Pyrite  is  an  undesirable  mineral  in  either  limestone  or  dolomite. 
Chert   or   flint   should   likewise   be   avoided.     It   sometimes' 
forms  lines  of  concretions  along  the  bedding  planes  and  causes 
the  stone  to  split  when  exposed  to  frost  action. 

Crushing  Strength.     Most  hard  limestones  show  a  good  crush- 
ing strength,  ranging  from  9000  to  12,000  pounds  per  square  inch. 
Fire  Resistance.     The  resistance  of  limestone  to  fire,  at  tem- 
peratures below  that  required  to  convert  the  stone  into  quick- 
lime, is  usually  fair,  although  lime  rock,  like  other  kinds  of  stone, 
is  apt  to  spall  badly  under  the  combined  attack  of  fire  and  water. 
Tests  of  Limestone.     There  are  few  complete  series  of  pub- 
lished tests,  but  the  following  table,  though  somewhat  incom- 
plete, may  serve  to  give  some  idea  of  their  variation. 


182 


BUILDING   STONES  AND   CLAY-PRODUCTS 


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LIMESTONES  AND  MARBLES 


Chemical  Composition.  The  following  analyses  are  given  for 
the  benefit  of  those  who  desire  to  see  the  range  in  chemical  com- 
position shown  by  limestones  which  are  used  for  structural  work : 


I. 

II. 

III. 

IV. 

Calcium  carbonate  (CaCOs) 

07    26 

ZA     C? 

81  43 

08    QI 

Magnesium  carbonate  (MgCO3)  .... 
Alumina  (A12O3)          j. 

0-37 
0.40 

39-41 

o.  26 

IS  -°4 

o.  t(7 

0.58 
O.63 

Ferric  oxide  (Fe2O3)  }  ' 
Silica  (SiO2)    

1.69 

3.96 

2.89 

O.  IO 

Water  (H2O) 

I     SO 

o  08 

I.  Bedford,  Ind.;    II.  Newburg,  N.  Y.;    III.  Spore,  Ohio;    IV.  Siluria,  Ala. 

Varieties  of  Limestone  and  Dolomites.  The  following  vari- 
ety names  include  those  not  uncommonly  found  in  the  literature. 
They  are  used  for  structural  or  ornamental  work  unless  other- 
wise stated.  These  latter  exceptions,  although  not  properly 
belonging  here,  are  mentioned  because  their  value  is  sometimes 
misjudged. 

Chalk  is  a  fine,  white,  earthy  limestone,  composed  chiefly  of 
the  shells  of  microscopic  animals.  It  is  of  no  structural  value. 

Coquina  is  a  loosely  cemented  shell  aggregate,  like  that  found 
near  St.  Augustine,  Fla.  The  Spaniards  used  blocks  of  this  for 
purposes  of  construction. 

Dolomite  is  a  rock  composed  of  carbonate  of  lime  and  carbonate 
of  magnesia,  in  the  proportions  of  54.35  per  cent  of  the  former 
and  45.65  per  cent  of  the  latter.  It  may  contain  clayey  impuri- 
ties, and  grades  into  limestone. 

Fossiliferous  Limestone.  A  general  term  applied  to  those  lime- 
stones which  contain  fossil  remains,  such  as  shells  and  corals. 
If  the  stone  is  dense  and  capable  of  taking  a  polish,  the  lines  of 
these  fossils  often  add  to  the  beauty  of  the  stone. 

Hydraulic  limestone  is  clayey  limestone  containing  over  ten 
per  cent  of  clay  impurities.  It  is  not  used  for  building  stone. 

Lithographic  limestone  is  an  exceedingly  fine-grained,  crystal- 
line limestone.  It  is  used  for  lithographic  and  not  for  structural 
work.  The  thin,  impure  layers  overlying  the  lithographic  rock 
in  the  Bavarian  quarries  are  locally  used  as  roofing  tiles. 


184  BUILDING   STONES   AND   CLAY-PRODUCTS 

Magnesian  or  Dolomitic  Limestone.  This  is  a  rock  intermedi- 
ate in  composition  between  a  pure  dolomite  and  a  pure  calcite 
limestone.  It  may  show  a  variable  composition. 

Marble.  This  properly  includes  all  crystalline  limestones, 
whose  grains  may  be  either  calcite  or  dolomite.  The  term 
marble  as  used  commercially  has  a  somewhat  broader  meaning, 
since  it  includes  all  limestones  that  will  take  a  polish.  It  may, 
therefore,  include  hard,  dense,  non-crystalline  lime  rocks. 

Oolitic  Limestone.  A  limestone  made  up  of  small  rounded 
grains  of  concretionary  character.  The  Bedford  limestone  of 
Indiana  and  some  of  the  soft  French  limestones  are  in  part  of 
this  character. 

Travertine,  calcareous  tufa  or  calc  sinter,  is  a  limestone  de- 
posited by  streams  and  springs.  It  may  be  compact,  but  is 
usually  quite  porous,  and  sometimes  hard  enough  to  be  used  for 
building  purposes.  No  deposits  of  commercial  value  are  found 
in  the  United  States,  but  an  extensive  deposit  is  worked  near 
Tivoli  in  Italy,  and  was  used,  for  example,  in  the  cathedral  of 
St.  Peter  in  Rome.  The  interior  of  the  new  Pennsylvania 
Railroad  Station  in  New  York  City  is  covered  with  it.  Stalac- 
tites and  stalagmites  are  lime  carbonate  deposits,  formed  re- 
spectively on  the  roof  and  floor  of  caves.  They  are  compact 
and  crystalline,  and  yield  a  form  of  marble  sometimes  incorrectly 
called  onyx. 

DISTRIBUTION  OF  LIMESTONES  IN  THE  UNITED  STATES. 

Limestones  are  found  in  many  states,  and  in  all  geological 
formations  from  the  Cambrian  up  to  the  Tertiary.  Those  found 
in  the  older  geologic  formations  are  on  the  whole  denser  and 
harder  than  those  found  in  the  younger  ones. 

Although  many  large  quarries  have  been  opened  to  supply  a 
local  demand,  the  product  is  shipped  to  a  distance  from  only  a 
few  localities.  At  present  the  Bedford,  Ind.,  limestone  is  per- 
haps the  most  widely  used  in  the  United  States,  and  is  even 
shipped  to  Canada. 

Only  a  few  of  the  more  important  regions  can  be  mentioned 
here.  (See  Plate  XXXII.) 


115° 


111° 


103° 


10? c 


0   50  100     200 

PLATE  XXXII.  — Map  showing  limestone  a 


400  500  600 

of  United  States.     (After  U.  S.  Geol.  Surv.) 


LIMESTONES  AND  MARBLES  189 

NEW  YORK. 

This  state  contains  an  abundance  of  hard,  compact  limestone, 
suitable  for  building  purposes,  but  most  of  it  is  used  only  locally 
for  foundation  work,  or  ashlar  blocks.  The  distribution  of 
limestones  is  shown  on  the  map  (Plate  XXXII).  The  Helder- 
berg  limestone  formation  extending  westward  through  the  central 
part  of  the  state;  the  Niagara  limestone  between  Rochester  and 
Lockport;  the  Trenton  limestone  of  the  Lake  Champlain  belt 
and  similar  dark  limestones  on  the  northwest  side  of  the  Adiron- 
dack region  are  all  good  building  stones.  The  crystalline  lime- 
stones are  referred  to  under  marbles.  The  value  of  the  stone 
quarried  for  road  making  and  rubble  far  exceeds  the  value  of 
that  quarried  for  building  purposes. 

NEW  JERSEY. 

This  state  contains  two  well-known  limestones,  occurring 
chiefly  in  Sussex  and  Warren  counties.  Of  these  the  most 
important  is  the  Kittatinny  blue  limestone.  This  is  massive,  fine 
grained,  usually  of  a  quite  uniform,  bluish  gray  color,  but  varies 
in  places  to  nearly  white,  or  to  dark  grayish  black.  It  may  carry 
seams  of  chert,  but  has  been  used  locally  throughout  the  region 
of  its  occurrence  and  is  of  good  durability. 

Examples.  —  Presbyterian  Chapel,  Newton;  Locke  Hall,  Blair  Academy, 
Blairstown;  Clinton  Hall,  same. 

PENNSYLVANIA. 

A  vast  amount  of  limestone  is  quarried  in  this  state  for  flux, 
roads  and  railroad  ballast.  The  amount  extracted  for  building 
purposes  is  comparatively  small. 

A  crystalline  limestone,  more  properly  described  under  marble, 
is  quarried  in  Montgomery,  Lancaster  and  other  counties  of 
southeastern  Pennsylvania.  It  is  of  a  variable  color  and  texture 
and  is  used  chiefly  for  ordinary  construction  work. 

In  the  central  and  western  part  of  the  state  there  are  a  number 
of  limestone  formations,  of  variable  character,  and  not  usually 
of  much  thickness.  They  are  of  value  only  for  local  use. 


EQO  BUILDING  STONES  AND   CLAY-PRODUCTS 

MARYLAND. 

Limestones  are  abundant  in  Maryland,  but  most  of  these  have 
not  been  quarried  except  for  local  use.  One  of  the  most  impor- 
tant is  that  from  the  Shenandoah  formation  of  the  Hagerstown 
and  Frederick  valleys. 

The  stone  is  of  a  deep  blue  color  when  freshly  quarried,  but 
upon  exposure  changes  slowly  to  a  dove  gray.  The  stone  is  at 
many  points  covered  by  residual  clay. 

This  same  formation  is  important  at  other  points  in  the  Great 
Valley  to  the  southward. 

VIRGINIA. 

The  most  important  limestone  formations  are  found  west  of 
the  Blue  Ridge.  That  known  as  the  Shenandoah  limestone  is 
the  most  persistent  one  in  the  state,  being  the  underlying  rock 
of  the  Great  Valley. 

The  rock,  which  often  contains  chert,  varies  from  a  finely 
granular,  dark  blue,  nearly  black  rock,  to  a  fairly  coarse,  light 
gray,  crystalline  one.  The  most  important  member  for  the  pro- 
duction of  building  stone  is  the  Natural  Bridge  limestone,  which 
is  a  heavy  bedded,  dark  blue  to  gray,  magnesian  limestone. 
Quarries  have  been  opened  up  in  a  number  of  points  in  the  Great 
Valley  for  local  use. 

WEST  VIRGINIA. 

This  state  contains  several  belts  of  limestone,  but  they  have 
not  been  much  used  except  for  foundations,  although  it  is  said 
some  of  the  quarries  would  yield  a  durable  and  beautiful  rock. 
The  oolitic  limestone  of  Greenbrier  County  is  thought  to  be  of 
value  for  ornamental  work. 

ALABAMA. 

The  best  limestones  are  found  in  the  Lower  Carboniferous  and 
Trenton  formations;  and  quarries  have  been  opened  in  Marshall, 
Colbert,  Franklin,  Bibb,  Shelby,  Jefferson,  St.  Clair,  Talladega, 
Calhoun,  DeKalb  and  Etowah  counties. 

The  best  known  is  an  oolitic  limestone  of  Rockwood,  Franklin 
County. 


LIMESTONES  AND  MARBLES  IQI 

In  southern  Alabama,  the  St.  Stephen's  limestone,  known  as 
" chimney  rock,"  is  somewhat  extensively  employed.  This  is  a 
soft,  somewhat  chalky,  white  limestone,  which  is  quarried  by 
cross-cut  saw,  and  shaped  with  saw,  hatchet  and  plane.  It  is 
used  mainly  for  chimneys. 

FLORIDA. 

Little  limestone  is  quarried  in  this  state.  On  Anastasia 
Island,  about  two  miles  from  St.  Augustine,  a  good  deal  of 
coquina  (p.  185)  was  formerly  quarried.  It  was  used  in  the  con- 
struction of  the  old  city  of  St.  Augustine  and  of  Fort  Marion. 

A  somewhat  soft  oolitic  limestone  occurs  in  southern  Florida, 
and  has  been  quarried  at  Key  West. 

ILLINOIS. 

Cook  County  is  the  most  important  producer,  limestone  being 
quarried  near  Chicago. 

In  Will  County,  the  Niagara  stone  is  quarried  in  the  vicinity 
of  Lemont  and  Joliet.  The  stone  is  a  fine-grained,  even- textured, 
light  gray  rock,  in  massive  beds,  and  easily  quarried.  It  also 
works  readily  to  a  smooth  surface,  but  does  not  take  a  polish. 
It  can  be  used  for  ornamental  work.  The  stone  is  said  to  carry 
considerable  quarry  water,  and  hence  cannot  be  quarried  in 
freezing  weather. 

Other  quarries  are  worked  in  Kankakee,  Adams  and  Madison 
counties. 

INDIANA. 

The  most  important  quarrying  district  of  Indiana  lies  in  Owen, 
Monroe  and  Lawrence  counties,  in  the  southwest  part  of  the 
state,  and  supplies  the  well-known  Bedford  stone,  which  has 
acquired  a  wide  and  favorable  reputation  for  building  and 
ornamental  purposes. 

The  Bedford  stone  is  a  granular  stone  of  fine  to  medium  grain, 
and  either  oolitic  texture  or  made  up  mostly  of  minute  fossils. 
In  the  trade  the  color  is  classed  as  blue,  buff  or  mixed.  The 
first  is  supposed  to  be  the  original  color,  and  the  buff  to  have 
been  derived  from  it  on  weathering,  but  this  difference  in  color 
is  sometimes  perceptible  only  in  the  quarry  or  in  large  blocks  and 


192  BUILDING  STONES  AND   CLAY-PRODUCTS 

not  in  hand  specimens.  The  stone  hardens  on  exposure  but 
should  be  laid  on  bed,  as  carelessness  in  laying  is  said  to  have 
caused  loss.  The  effect  of  lichens,  vines  and  plants,  is  also  said 
to  cause  discoloration  and  disintegration. 

Owing  to  its  comparative  softness  and  evenness  the  stone  can 
be  sawn  or  dressed  for  ornamental  work. 

Examples.  —  Library,  Columbia  University,  New  York  City;  City  Hall,  Indian- 
apolis, Ind.;  Pro-Cathedral,  Minneapolis,  Minn.;  Capitol,  Frankfort,  Ky.;  new 
wing  Metropolitan  Museum  of  Art,  New  York  City;  Eighth  Church  of  Christ, 
Scientist,  Chicago,  111. 

KENTUCKY. 

The  oolitic  limestone  known  as  the  Bowling  Green  Oolitic 
from  Warren  County,  is  second  in  importance  to  the  Bedford, 
Ind.,  stone.  Indeed,  the  two  are  similar  in  appearance  and 
general  character,  and  occur  in  the  same  formation.  It  is  a 
massive  stone,  the  quarried  blocks  averaging  4  by  5  by  8  feet, 
and  can  be  placed  in  any  position  in  building.  The  fresh  stone 
is  a  buff-gray,  but  changes  on  exposure  to  very  light  gray.  This 
bleaching,  which  is  said  to  be  due  to  the  evaporation  of  a  small 
amount  of  light,  volatile  petroleum,  may  extend  in  twenty-five 
feet  from  the  outcrop. 

Examples.  —  Custom  House  and  Carnegie  Library,  Nashville,  Tenn.;  Custom 
House,  Mobile,  Ala.;  Residence  of  A.  M.  Lathrop,  Washington,  D.  C. 

Other  limestones  occur  in  the  state  and  have  a  local  value. 

OHIO. 

The  numerous  limestones  and  dolomites  occurring  in  the  state 
are  used  to  some  extent  for  foundation  work,  paving  and  flagging, 
but  their  main  use  is  for  lime  manufacture  and  flux  and  crushed 

stone. 

WISCONSIN. 

According  to  Buckley  a  large  part  of  Wisconsin  is  underlain  by 
limestone,  which  extends  in  a  broad  belt  through  the  eastern, 
southern  and  western  parts  of  the  state,  and  in  formations  known 
as  Lower  Magnesian,  Trenton  and  Niagara. 

We  thus  have  a  variety  of  stones,  but  they  are  mostly  dolomites. 

In  some  localities  the  stone  is  coarse  grained  and  sugary;  while 
in  others,  it  is  dense  and  finely  crystalline.  The  limestone  may 


PLATE  XXXIII.  —Statue  of  Labor,  cut  in  "Old  Hoosier,"  Light  Blue,  Bedford 
Limestone,  for  City  Investment  Building,  New  York  City.  (Photo  from 
Bedford  Quarries  Company.) 


LIMESTONES  AND  MARBLES  195 

vary  even  in  different  parts  of  the  same  formations.  The  colors 
vary  from  buff  or  straw  yellow  to  dark  bluish  gray. 

The  largest  quarries  in  the  state  are  in  the  limestone  region, 
but  the  stone  is  not  used  exclusively  for  building  purposes. 

The  lower  magnesian  limestone  quarried  at  Bridgeport, 
Trempeleau  and  Maiden  Rock  furnishes  a  good  stone  for  all 
ordinary  purposes. 

The  Trenton  gives  satisfaction  where  there  is  little  or  no 
danger  from  freezing,  under  which  action  it  opens  up  along  bed. 

The  Niagara  is  quarried  at  Wauwatosa,  Lannon,  Genessee, 
Marblehead,  Sturgeon  Bay  and  Knowles. 

Examples.  —  Lower  magnesian  limestone:  Wisconsin  State  Capitol,  Madison, 
Wis.;  Normal  School  Building,  Madison,  S.  Dak.;  Minneapolis  stone  arch  bridge. 
Trenton  limestone:  Post  Office,  Milwaukee,  Wis.  Niagara  limestone:  Loan  and 
Trust  Building,  Milwaukee,  Wis.;  Beloit  College  Chapel,  Beloit,  Wis.;'Court  House,, 
Waukesha,  Wis. 

MINNESOTA. 

The  Minnesota  limestones  are  all  dolomitic,  and  the  best  ones 
for  building  purposes  are  quarried  near  Mankato  and  Kasota 
in  the  south-central  portion  of  the  state  near  the  Minnesota 
River.  These  stones,  which  are  very  fine  grained  and  crystalline, 
resemble  sandstone  in  appearance  and  have  an  excellent  reputa- 
tion. They  are  usually  some  shade  of  yellow  or  yellowish 
brown,  and  take  a  fair  polish. 

Examples.  —  This  dolomite  was  extensively  used  for  interior  work  in  the  Minne- 
sota State  Capitol,  and  much  of  it  has  been  shipped  to  other  states.  It  was  also 
employed  for  much  of  the  interior  work  of  St.  John  the  Divine  Cathedral,  in  New 
York  City.  The  U.  S.  Post  Office  Building  at  Aberdeen,  S.  Dak.,  is  faced  with 
Kasota  cut  stone,  and  much  of  the  marble  wainscoting  in  the  Minnesota  State 
Capitol  at  St.  Paul  is  polished  Kasota  stone. 

Much  dolomitic  limestone  has  been  quarried  for  local  use 
around  the  "  Twin  Cities."  It  is  used  chiefly  for  foundations,  but 
splits  rapidly,  is  full  of  concretions  and  not  of  a  pleasing  color. 

The  Mankato  stone,  which  is  used  largely  for  massive  masonry, 
is  a  buff  color,  w^hile  the  Kasota  rock  is  used  for  finer  building 
purposes  and  is  a  light  pink  shade. 

Kasota  cut  stone,  tool  faced,  is  approximately  $1.25  per  cubic 
foot;  polished  work,  50  to  75  cents  per  square  foot,  depending 
on  color. 


196  BUILDING  STONES  AND   CLAY-PRODUCTS 

MISSOURI. 

Limestone  formations  are  known  to  underlie  an  extensive  area 
in  Missouri,  probably  two-thirds  of  them  belonging  to  the  Lower 
Carboniferous  formation. 

Of  these  the  Burlington  formation  is  the  most  important,  since 
it  supplies  the  greatest  amount  of  cut  and  sawed  stone  of  any 
of  the  formations  in  the  state. 

This  stone,  which  is  extensively  quarried  around  Carthage 
as  well  as  Phenix  and  Hannibal,  is  of  a  uniform  light,  almost 
white  color,  and  is  strong  and  durable.  It  can,  moreover,  be 
quarried  in  blocks  of  large  dimensions. 

The  stone  is  more  difficult  to  cut  and  dress  than  Bedford  stone, 
but  is  lighter  and  more  uniformly  colored,  also  stronger  and  denser. 

It  takes  a  good  polish  and  has  been  much  used  in  monumental 
work,  but  one  difficulty  has  been  the  obtaining  of  large  pieces  free 
from  suture  joints.  Flint  nodules  are  found  at  definite  horizons 
in  the  formation,  and  have  to  be  avoided. 

Examples.  —  Carnegie  Library,  Joplin,  Mo.;  Stillwell  Hotel,  Pittsburgh,  Kans.; 
Public  Library,  Kansas  City,  Mo.;  Ex-Confederate  Monument,  Ft.  Smith,  Ark. 

While  this  is  the  most  important  limestone  quarried  in  the 
state,  there  are  others  which  are  worked  to  a  minor  extent. 

In  southern  Missouri  the  dolomites  of  the  Cambro-Ordovician 
formation  are  extensively  used  for  building.  This  includes  the 
so-called  cotton  rock  quarried  around  Jefferson  City. 

In  southern  Missouri  there  are  also  finer-grained  limestones, 
somewhat  resembling  marble. 

Around  Stee  Genevieve  the  Trenton  limestone  supplies  a  good 
building  material,  but  the  same  formation  around  St.  Louis  is 
soft  and  undesirable. 

Near  St.  Louis,  the  St.  Louis  limestone  is  extensively  quarried 

for  rough  masonry. 

IOWA. 

Limestones  form  the  most  important  building  stones  of  the 
state,  and  some  of  them  are  dolomitic  in  their  character,  but  all 
are  worked  chiefly  for  local  use. 

KANSAS. 
This  state  contains  some  limestones,  but  few  are  of  importance. 


LIMESTONES  AND  MARBLES  197 

TEXAS. 

Limestones  suitable  for  building  purposes  occur  abundantly 
in  the  vicinity  of  Austin,  Texas.  They  are  known  as  the  Glen 
Rose  limestone,  northwest  of  Austin;  the  Edwards  limestone, 
outcropping  along  the  Colorado  River,  and  the  Austin  chalk, 
within  the  city  limits. 

CORDILLERAN  REGION. 

In  the  territory  extending  from  the  eastern  edge  of  the  Rocky 
Mountains  to  the  Pacific  Coast,  there  are  scattered  limestone 
formations,  but  few  are  quarried,  except  for  local  purposes,  the 
more  abundant  igneous  rocks  being  often  preferred.  Many  of 
those  occurring  in  this  region  lack  development  partly  because 
there  is  no  demand  for  them. 

Limestones  are  known  in  Colorado  but  they  are  usually  too 
impure  and  not  massive  enough  for  building  purposes. 

MARBLES. 

Under  this  term  there  are  properly  included  those  limestones 
or  dolomites  which  have  a  crystalline  texture  and  are  susceptible 
of  taking  a  good  polish.  The  term  marble  has,  however,  come 
to  be  somewhat  loosely  used  in  the  trade,  and  is  often  applied  to 
any  limestone  which  will  take  a  polish,  whether  it  is  crystalline 
or  not.  Marbles  are  used  chiefly  for  ornamental  work  and  the 
better  grades  of  construction. 

Mineral  Composition.  Marbles,  when  pure,  are  composed  of 
calcite,  dolomite  or  a  mixture  of  the  two.  Other  minerals  are 
not  infrequently  present  and  are  often  to  be  regarded  as  injuri- 
ous impurities.  The  following  are  not  uncommon. 

Mica.  This  occurs  usually  in  fine  scales,  not  always  of  the 
same  species,  and  these  small  scales  are  present  often  in  bands, 
usually  of  a  wavy  nature,  or  in  blotches.  Mica  in  small  amounts 
is  not  very  harmful,  but  if  abundant  it  interferes  with  the  con- 
tinuity of  the  polish  and  lowers  the  weather-resisting  qualities 
of  the  stone,  the  mica  decaying  and  leaving  a  pitted  surface. 
Marbles  containing  an  abundance  of  mica  are,  therefore,  not 
adapted  to  exterior  work  in  a  severe  climate.  It  is  no  doubt  true 


BUILDING  STONES  AND   CLAY-PRODUCTS 

that  the  bands  and  cloudings  of  mica  often  add  to  the  beauty  of 
the  stone,  but  it  is  better  to  sacrifice  a  little  ornamental  value 
rather  than  to  select  a  stone  which  is  sure  to  disintegrate  in  the 
course  of  a  few  years.  Architects  would  do  well  to  give  more 
heed  to  this  matter  than  many  of  them  do.  The  author  has 
observed  columns  of  cipolino  marble,  in  New  York  City,  which 
were  seriously  affected  after  three  years'  exposure  to  the  weather. 

Pyrite  is  present  in  small  scattered  grains  in  some  marbles. 
Such  stones  should  be  avoided  as  much  as  possible,  as  pyrite 
rusts  easily  and,  in  so  doing,  yields  sulphuric  acid  which  still 
further  attacks  the  stone. 

Tremolite  (Plate  XXXI,  Fig.  2)  is  a  mineral  impurity  of  some 
dolomitic  marbles  and  its  light  colored,  silky  lustred  grains,  when 
fresh,  are  easily  recognizable.  It  weathers  somewhat  easily  to  a 
clayey  material,  so  that,  if  abundant,  the  surface  of  the  stone  may 
become  pitted  as  the  tremolite  weathers  out.  In  some  quarries 
the  tremolite  has  been  found  to  occur  abundantly  in  certain  parts 
of  the  quarry. 

Quartz,  may  occur  in  some  marbles  as  veins,  concretions  or 
thin  layers.  Such  stone  should  be  rejected. 

Carbon  is  the  cause  of  the  gray,  blue-gray  and  black  color  seen 
in  many  marbles  (Plate  XXXVI,  Fig.  2).  It  may  color  them 
uniformly  or  form  cloudy  patches  and  bands,  thus  adding  greatly 
to  the  beauty  of  the  stone. 

Iron  oxide  is  found  in  many  marbles,  and  is  responsible  for  the 
beautiful  red,  yellow,  brown  and  pink  colorings  shown  by  many 
of  them. 

Color.  Marbles  show  a  great  range  of  colors;  some  are  snow 
white,  others  gray  to  black;  still  others  may  show  varying  and 
often  beautiful  shades  of  red,  vpink,  yellow,  green,  brown,  etc. 

Texture.  The  texture  of  marbles  may  range  from  those  of 
exceedingly  fine  grain  to  those  which  are  very  coarse,  having 
grains  a  quarter  of  an  inch  in  diameter.  The  medium  to  fine- 
grained ones  are  to  be  preferred. 

Some  ornamental  marbles  show  a  brecciated  structure.  That 
is,  they  are  made  up  of  angular  particles  of  crushed  rock,  the 
interstices  between  them  being  filled,  in  part,  by  secondarily 


PLATE  XXXIV.  —  A  decorative  marble,  showing  a  brecciated  structure. 


199 


LIMESTONES  AND  MARBLES 


201 


deposited  mineral  matter. 
Such  stones  are  often  of 
great  ornamental  value,  but 
they  lack  in  durability  and 
should  not  be  used  for  exterior 
work  in  a  severe  climate,  a 
fact  too  often  overlooked  by 
many  architects. 

Weathering  Qualities. 
What  has  been  said  regard- 
ing the  weathering  qualities 
of  limestone  is  equally  true  of 
the  marbles.  It  may  be  added 
that  those  with  a  brecciated 
structure  and  of  micaceous 
character  are  much  less  dur- 
able than  the  average  lime- 
stone. 

Absorption.  The  absorp- 
tion of  marbles  is  always  low, 
usually  under  one  per  cent. 

Crushing  and  Transverse 
Strength.  A  few  tests  taken 
from  different  sources,  are 
given  in  the  table  printed 
below. 

Uses  of  Marbles.  Marbles 
are  being  used  in  increasing 
quantities  for  ordinary  struc- 
tural work,  although  many  of 
the  lighter  colored  ones  soon 
become  soiled  by  dust  and 
smoke.  The  product  of  many 
quarries,  especially  the  Ver- 
mont ones,  is  well  adapted  to 
monumental  purposes,  as  are 
also  those  from  Georgia. 


!> 

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C/2 

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<N  IN   <N   (N      •      •   N   CS      • 

U 
If 

N§- 

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o'oo 

|i 

<J  S  »- 

[MM   M 

CM 

"S 

Remarks. 

'  '  Kennesaw  Marble  "  
White... 

Blue  
Richville  white  marble.  .  .  . 

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n 

linn  i|j 

|; 

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<o 

M«5 

QNOOOO^O 

8S8S&2&5& 

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M««  |«« 

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i 

III? 

1 

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OcHOc^  : 

H 

Location  of  quarry. 

>     :  :  :  : 

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«  b    _r  :jj  ;Z4. 

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SI^IIJIII 

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202  BUILDING   STONES  AND   CLAY-PRODUCTS 

Among  the  other  uses  of  marble  are  its  application  for  wain- 
scoting and  paneling,  floor  tiles,  electrical  switchboards  and 
sanitary  ware.  If  used  for  tiling  floors  it  is  often  preferable  to 
use  but  one  kind,  as  marbles  of  different  colors  may  be  of  unequal 
hardness,  and  hence  a  floor,  over  which  there  is  much  passing, 
may  wear  uneven  in  a  comparatively  short  time.  Many  of  the 
black  and  white  tiled  marble  floors  show  this.  The  demand  for 
marble  tops  for  tables  and  washbasins  is  probably  decreasing. 

Many  beautiful  decorative  effects  are  produced  by  sawing  a 
slab  of  colored  or  patterned  marble  in  two  or  more  slices  and 
matching  these  together  (Plate  XXXV). 

Distribution  of  Marbles  in  the  United  States.  Marbles  are 
less  widely  distributed  than  limestones,  since  they  occur  almost 
exclusively  in  areas  of  metamorphic  rock.  Most  of  those  quarried 
are  white,  few  being  of  variegated  color.  Indeed,  the  larger 
part  of  the  beautiful  decorative  ones  with  which  most  of  us  are 
familiar  are  imported  from  foreign  countries. 

Vermont  leads  all  other  states  in  the  quarrying  of  marble,  but 
Georgia  and  Tennessee  are  also  important  producers. 

The  more  important  occurrences  are  referred  to  below. 

VERMONT. 

The  Vermont  marble  deposits  begin  on  the  south  at  Dorset 
Mountain  and  extend  northward  in  a  narrow  belt  through 
Wallingford,  West  Rutland,  Pittsford  and  Brandon  to  Middle- 
bury.  These  are  all  true  marbles  or  metamorphosed  limestones. 
Another  important  locality  has  been  opened  up  farther  north  at 
Swanton,  but  this  is  not  a  true  marble. 

The  marble  used  for  building  purposes  varies  from  75  cents 
to  $2.00  per  cubic  foot,  while  that  for  monumental  work  may 
bring  from  $5  to  $7,  and  statuary  marble  as  much  as  $12. 

Those  marbles  quarried  at  Dorset  are  more  coarsely  crystal- 
line than  those  quarried  in  the  West  Rutland  area. 

It  can  be  said  that  in  general  the  Vermont  marbles  usually 
show  a  bluish  gray  or  whitish  ground,  the  latter  often  showing 
a  pinkish  or  creamy  shade,  and  traversed  by  veins  or  markings, 
more  or  less  distinct,  of  a  green  or  brown  color. 


fl 

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h    PH 


203 


— N 


PLATE  XXXVI,  Fig.  i.  —  White  marble,  Vermont. 


PLATE  XXXVI,  Fig.  2.  —  Gray  marble,  Vermont.     (The  color  is  due  to 
carbonaceous  matter.)  205 


LIMESTONES   AND   MARBLES  207 

Not  infrequently  several  different  varieties  or  shades  are  found 
in  the  same  quarry.  The  following  section  brings  this  point  out 
well,  and  shows  the  section  found  in  the  West  Rutland  quarries 
of  the  Vermont  Marble  Company. 

Blue  marble,  top  )  20  feet 

White  marble        f 

Green  striped 2  feet. 

White  statuary 5-6  feet. 

Striped  monumental 2-6  feet. 

White  statuary 3-6  feet. 

Layer  partly  green,  partly  white 4  feet. 

Green  and  white,  "  Brocadillo  " 2^-3  feet. 

Crinkly,  siliceous  layer,  half  light,  half  dark 2-3  feet. 

Light  and  mottled 4-6  feet. 

Green  striped 6  inches. 

White i\  inches. 

Half  dark  green,  half  white 3-6  inches. 

Italian  blue 15-20  inches. 

Mottled  limestone 

The  following  are  varieties  quarried  in  Vermont : 

LIGHT  MARBLES. 

Best  Light  Cloud  Rutland.  Very  light,  mostly  white,  with  very 
indistinct  veinings,  which  show  little,  except  on  a  polished  sur- 
face. Quarried  at  West  Rutland  by  Vermont  Marble  Company. 

Blue  Building.  A  bluish  gray  stone,  with  whitish  spots,  and 
occasional  white  veins.  Mainly  for  building,  but  also  polishes. 
Quarried  at  Fowler  by  Rutland-Florence  Marble  Company. 

Brandon- Italian.  Resembles  ordinary  veined  imported  Italian. 
General  ground  white,  with  indistinct  dark  bluish  veins  or  lines 
or  sometimes  spots  or  blotches.  Quarried  by  Brandon-Italian 
Marble  Company. 

Brandon- Italian,  High  Street  Variety.  Similar  to  preceding, 
but  usually  darker.  Quarried  by  same  company. 

Brocadillo.  Might  be  classed  with  fancy  varieties.  Re- 
sembles Listavena,  but  is  darker  and  has  greater  abundance  of 
green  veins,  which  are  sometimes  very  abundant  and  pro- 
nounced. Quarried  at  West  Rutland  by  Vermont  Marble 
Company. 

Dorset  Dark  Green  Vein.  Nearly  white  marble  in  some 
examples  and  greenish  in  others.  White  ground,  cut  by  numer- 
ous green  lines,  veins,  bands  or  blotches,  so  arranged  that  slabs 


208  BUILDING   STONES  AND   CLAY-PRODUCTS 

can  be  matched  to  form  figures  in  a  panel.     There  are  also 
blotches. 

Examples.  —  Interior  paneling  of  Albany  Commercial  Bank;  Four-piece  panels, 
some  of  the  latter  being  18  feet  high  and  13  feet  wide;  Twenty-five  columns  in  exhi- 
bition room  of  New  York  City  Library;  Interior  of  American  Trust  and  Securities 
Building,  Chicago. 

Dorset  White.  Appears  pure  white  from  distance,  but  upon 
close  examination  shows  delicate  light  brown  or  smoky  bands 
or  veins.  The  Dorset  marbles  are  harder  and  more  coarsely 
crystalline  than  those  of  the  Rutland  district. 

Example.  —  The  New  York  Public  Library  Building  on  Fifth  Avenue  is  built 
of  this  marble. 

Florence.  For  monuments  and  building.  Bluish  white  ground 
clouded  and  veined  with  dark  shades,  varying  from  smoky  to 
black.  Quarried  at  Fowler  by  Rutland-Florence  Marble  Com- 
pany. 

Gray  Building.  General  tone  bluish  gray,  slightly  mottled 
with  white  and  veined  with  dark  shades.  Veins  usually  quite 
fine.  Quarried  at  West  Rutland  by  Vermont  Marble  Company. 

Italio.  A  moderately  light  marble,  with  bluish  white  ground, 
and  darker  bluish  cloudings.  Quarried  at  Columbian  quarry, 
Proctor,  by  Vermont  Marble  Company. 

Light  Florence.  Resembles  some  of  the  light  Italian  marbles. 
Ground  white  with  bluish  cast,  thickly  clouded  and  streaked 
by  dark  spots  and  lines.  Markings  more  regular  than  those  of 
many  Vermont  marbles.  Quarried  at  Fowler  by  the  Rutland- 
Florence  Marble  Company. 

Light  Green  Cloud.  A  Dorset  marble  of  clear  white  ground, 
with  scattered  greenish  clouds  and  patches.  Some  of  these  are 
dark.  A  good  building  marble,  but  used  especially  in  interiors. 
Quarried  at  Dorset  by  the  Norcross-West  Marble  Company. 

Light  Sutherland  Falls.  Nearly  pure  white  ground,  with 
veins,  usually  of  a  bluish  white  color.  Quarried  at  Proctor. 

Listavena.     Green  and  white  bands.     West  Rutland. 

Mountain  White.  Very  light,  with  occasional  brownish  veins. 
Quarried  at  Danby  by  Vermont  Marble  Company.  Much  has 
been  used  in  New  Senate  Building  in  Washington,  including 
sixty  large  columns. 


PLATE  XXXVII,  Fig.  i.  —  Quarries  in  Travertine  near  Tivoli,  Italy. 
(Photo  by  J.  C.  Branner.) 


PLATE  XXXVII,  Fig.  2.  —  Quarry  of  Vermont  Marble  Company,  Proctor,  Vt. 
(Photo  loaned  by  Vermont  Marble  Company.) 

209 


PLATE  XXXVIII.  —  Kimball  Monument,  Chicago,  111.     Done  in  Vermont  white 
marble.     (Photo  loaned  by  Vermont  Marble  Company.) 


211 


LIMESTONES  AND   MARBLES  213 

Pitts] 'or d- Italian.  Light  with  yellowish  brown  lines.  Quar- 
ried at  Pittsford,  by  Rutland-Florence  Marble  Company. 

Pittsford  Valley.      First  quality.     Resembles  Sutherland  Falls. 

Plateau  White.  Very  light  with  irregular  creamy  and  greenish 
bands.  A  hard,  durable  marble. 

Example.  —  New  Harvard  Medical  Buildings.  Quarried  at  Dorset  by  Norcross- 
West  Marble  Company. 

Statuary.    A  very  white  layer,  quarried  at  West  Rutland. 

DARK  MARBLES. 

These  include  those  in  which  black,  dark  green  or  blue  pre- 
dominate over  lighter  shades  or  white.  They  are  not  so  com- 
monly used  for  building  stones  as  the  lighter  varieties,  but  are 
very  effective  when  rock  faced.  Their  main  use  would  seem  to 
be  for  interior  finish.  They  are  occasionally  used  for  monuments. 
Some  of  the  black  ones  are  not  true  metamorphic  limestones. 

Black  or  Fisk  Black.  This,  properly,  is  a  limestone.  It  is  a 
dark  gray  or  gray-black  limestone.  Not  extensively  used. 

Dark  Florence.  Bluish  ground,  with  lighter  veins.  Quarried 
at  Fowler,  by  Rutland-Florence  Marble  Company. 

Dark  Vein  Esperanza.  One  of  the  darker  Vermont  ones. 
West  Rutland. 

Dark  Vein  or  True  Blue.     West  Rutland. 

Extra  Dark,  Mottled  True  Blue. 

Extra  Dark,  Royal  Blue.  Darkest  marble  found  in  Rutland 
area. 

Other  varieties  are:  Extra  Dark  Vein  True  Blue;  Florentine 
Blue;  Highland  Blue;  Livido. 

ORNAMENTAL  OR  FANCY  MARBLES.     , 

Many  of  these  are  not  as  brightly  colored  as  some  of  the 
imported  ones,  but  they  often  show  very  decorative  effects. 
Among  them  may  be  mentioned : 

Molian. 

American  Pavonazzo.  Dark  green  veins  on  a  beautifully 
tinted  creamy  ground.  Quarried  at  West  Rutland  by  Vermont 
Marble  Company. 


214  BUILDING  STONES  AND    CLAY-PRODUCTS 

American  Yellow,  Pavonazzo.  Color  mainly  light  salmon,  with 
yellow  or  creamy  tints.  Quarried  at  West  Rutland  by  Vermont 
Marble  Company. 

Columbia  Listavena.  Light  yellow  ground,  with  veining  of 
gray,  light  brown  or  olive.  Quarried  at  West  Rutland  by 
Vermont  Marble  Company. 

Olivo.     A  Rutland  marble  similar  to  Brocadillo. 

Pink  Listavena.     Salmon  ground,  greenish  veins. 

Rosaro.     Light  yellow  with  delicate  light  olive  veins. 

Rubio.  Delicate  pink  ground  inclining  to  salmon,  and  in- 
definite veinings  of  light  green.  Quarried  at  West  Rutland. 

Verdoso.     A  green- shaded  West  Rutland  marble. 

Verdura.     A  greenish  marble  from  West  Rutland. 

Champlain  Marbles.  These  are  Lower  Cambrian  Red  Sand- 
rock,  being  an  unusually  calcareous  portion  of  the  same,  and  grade 
into  each  other.  With  one  exception  they  are  all  quarried  at 
Swanton  and  by  the  Barney  Marble  Company.  They  all  con- 
tain much  silica  and^iron  and  are  predominantly  shades  of  red 
and  white.  Being  harder  than  marble,  they  take  a  more  brilliant 
and  durable  polish.  For  the  same  reason  they  are  more  costly  to 
saw  and  finish,  but  are  used  for  flooring  and  wainscoting  all 
over  the  United  States.  The  varieties  are  Jasper,  Lyonnaise, 
Olive,  Royal  Red  and  Oriental  Verde. 


Examples  of  Vermont  Marbles.  —  The  following  list  of  buildings  constructed 
wholly  or  in  part  of  Vermont  marble,  have  been  supplied  by  several  companies: 

Vermont  Marble  Co.:  U.  S.  Post  Office  and  Court  House,  Worcester,  Mass.; 
Sutherland  Falls  marble;  U.  S.  Post  Office  and  Court  House,  Montpelier,  Vt., 
the  same;  Hart  Memorial  Library,  Troy,  N.  Y.,  Rutland  white  marble;  Clio  Hall, 
Princeton  College,  Princeton,  N.  J.,  Sutherland  Falls  marble;  Second  National 
Bank  Building,  Paterson,  N.  J.,  the  same;  Altar,  Church  of  the  Sacred  Heart, 
Shelby,  Ohio,  Rutland  white  marble;  Stock  Exchange,  Chicago,  111.,  restaurant 
and  ceiling,  Listavena  and  White;  Columbia  Bank,  Pittsburg,  Pa.,  all  interior 
finish  Brocadillo;  Hibbs  Building,  Washington,  D.  C.;  Planters  Loan  and  Savings 
Bank,  Augusta,  Ga.;  Interior  marble,  Office  Building,  House  of  Representatives, 
Washington,  D.  C.;  Marble  for  Gardens,  J.  D.  Rockefeller,  Pocantico  Hills,  N.  Y., 
Rutland-Florence  Marble,  Fowler,  Vt. 

Brandon-Italian,  Middlebury,  Vt. :  Exterior  Memorial  Church,  Middlebury; 
Public  School  Building,  Hudson,  N.  Y.;  Annex  to  Fanny  Allen  Hospital,  Burling- 
ton, Vt.  This  marble  is  used  mainly  for  interior  and  vaults. 


LIMESTONES  AND  MARBLES  215 

Examples  of  Cham  plain  Marbles.     The  following  list  is  supplied  by  the  company: 

Red  marble:  Government  Building,  Troy,  N.  Y.;  Metropolitan  Museum  of  Art, 
New  York  City;  Government  Building,  Denver,  Colo.;  Congressional  Library, 
Washington,  D.  C.;  Planters  Hotel,  St.  Louis,  Mo.;  Auditorium  Hotel,  Chicago, 
111.;  Union  Station,  Toronto,  Canada. 

Red  and  green  marble:  Erie  Savings  Bank,  Buffalo,  N.  Y.;  Albany  Savings 
Bank,  Albany,  N.  Y.;  Government  Building,  Omaha,  Neb.;  Philadelphia  Mint, 
Philadelphia,  Pa.;  New  St.  Charles  Hotel,  New  Orleans,  La. 

Green  marble:  New  Southern  Terminal  Station,  Boston,  Mass.;  Hotel  Raleigh, 
Washington,  D.  C.;  Pittsburg  and  Lake  Erie  Depot,  Pittsburg,  Pa. 

MASSACHUSETTS. 

A  rather  fine-grained,  snow-white  marble  has  been  quarried 
for  a  number  of  years  at  Lee  in  western  Massachusetts.  Its 
chief  use  is  for  structural  work. 

Examples.  —  Wings  of  Capitol,  Washington,  D.  C.;  Public  Buildings,  Phila- 
delphia, Pa.;  Court  House,  Baltimore,  Md.;  Metropolitan  Insurance  Building  and 
Clearing  House,  New  York  City;  State  House  Annex  and  new  Commonwealth 
Trust  Co.,  Building,  Boston,  Mass.;  Interior  work,  Gen.  Grant's  Tomb,  and  Plaza 
Hotel,  New  York  City. 

CONNECTICUT. 

In  northern  Litchfield  County,  near  East  Canaan,  a  white, 
moderately  coarse  dolomite  occurs,  but  it  has  been  little  worked 
in  recent  years.  The  stone  weathers  well,  but,  like  the  Lee 
(Mass.)  dolomite,  often  contains  crystals  of  tremolite. 

Example.  —  The  State  House  at  Hartford,  Conn. 
NEW  YORK. 

Southeastern  New  York  contains  a  number  of  beds  of  dolomite 
marble.  This  has  been  quarried  at  Tuckahoe,  Pleasantville  and 
South  Dover. 

The  Tuckahoe  stone  is  moderately  coarse  grained  and  pure 
white,  but  turns  grayish  on  exposure  to  the  air,  as  the  coarse- 
grained surface  catches  the  dust. 

Examples.  —  St.  Patrick's  Cathedral,  New  York  City;  Metropolitan  Life  In- 
surance Building,  New  York  City. 

The  South  Dover  marble  is  finer  grained  than  the  Tuckahoe, 
but  also  of  white  color.  It  has  been  used  mainly  for  ordinary 
structural  work. 

Examples.  —  Tiffany  Building,  New  York  City;  Essex  County  Court  House, 
Newark,  N.  J. 


2l6  BUILDING   STONES   AND    CLAY-PRODUCTS 

A  moderately  coarse-grained,  light  gray,  or  grayish  white 
dolomite  marble  is  quarried  near  Gouverneur,  St.  Lawrence 
County.  It  is  well  adapted  for  ordinary  structural  work,  and 
for  inscriptional  purposes  shows  a  good  contrast  between  the 
polished  and  hammered  surface. 

Some  dense  limestones,  susceptible  of  taking  a  good  polish, 
have  been  quarried  to  a  small  extent  in  Clinton  County,  near 
Plattsburg  and  Chazy.1 

The  one  known  as  Lepanto  marble  is  a  fine-grained  gray  stone, 
with  pink  and  white  fossil  remains.  The  other,  known  as  French 
gray,  is  more  uniformly  gray  and  bears  larger  fossils.  Both  are 
quite  ornamental,  but  their  use  has  declined. 

A  black  limestone  known  as  black  marble  has  been  quarried 

at  Glens  Falls. 

PENNSYLVANIA. 

A  white  dolomite  marble  of  sugary  texture  is  quarried  at 
Avondale,  Chester  County.  It  is  used  for  structural  work. 

There  are  a  number  of  occurrences  of  crystalline  limestone  in 
southeastern  Pennsylvania,  but  few  of  them  are  worked  for 

marble. 

MARYLAND. 

The  two  marble-producing  localities  are  Cockeysville  and 
Texas,  and  although  they  are  quite  close  together  the  marbles 
differ  from  each  other  in  purity  and  texture. 

The  Texas  stone  is  a  coarse-grained,  calcite  marble  and  is  not 
used  now  for  building  purposes,  although  some  of  it  was  quarried 
and  placed  in  the  lower  150  feet  of  the  Washington  monument.2 

The  Cockeysville  marble  is  a  fine-grained  dolomite,  well  adapted 
for  building  and  decorative  use.  It  is  clear  white  in  color  with 
occasional  streaks  of  pale  gray,  but  care  has  to  be  used  to  avoid 
streaks  of  silicate  minerals  which  occur  here  and  there  in  the 
quarry. 

Examples. — Washington  Monument,  Mt.  Vernon  Place,  Baltimore,  Md., 
erected  in  1829;  108  monoliths,  26  feet  long,  for  National  Capitol;  U.  S.  Post  Office 
Building,  Washington;  Drexel  and  Penn  Mutual  Insurance  Building,  Philadelphia, 
Pa.;  Spires  of  St.  Patrick's  Cathedral,  New  York  City;  Art  Museum,  Pan-American 
Exposition,  Buffalo,  N.  Y. 

1  Merrill,  "Stones  for  Building  and  Decoration."  2  Ibid. 


LIMESTONES  AND   MARBLES  217 

A  curious  stone  is  that  known  as  the  Calico  marble,  quar- 
ried at  the  Point  of  Rocks,  Frederick  County.  It  is  a  con- 
glomerate, made  up  of  limestone  pebbles  which  average  two 
to  three  inches  in  diameter.  The  rounded  and  angular  fragments 
are  gray  to  dark  blue  in  color.  The  pebbly  character  of  the  stone 
and  irregularity  in  hardness  make  it  difficult  to  polish  and  work. 

Example.  —  Columns  of  this  marble  are  in  the  old  House  of  Representatives 
now  used  by  the  Supreme  Court. 

VIRGINIA. 

While  crystalline  limestones  occur  in  Virginia,  still  the  state 
is  of  little  importance  as  a  marble  producer.  The  principal 
localities  found  west  of  the  Blue  Ridge  may  be  described  as 
follows : 

New  Market  and  Woodstock,  A  coarse-textured,  dun-colored 
marble,  capable  of  taking  a  good  polish;  New  Market,  A 
mottled  bluish  marble,  somewhat  coarser  grained  than  preced- 
ing; Buchanan,  Gray  marble  of  fine  gray  character;  Lex- 
ington, White,  fine-grained  marble,  capable  of  taking  a  good 
polish;  Giles  County,  Red  marble;  Blacksburg,  Black,  fine- 
grained marble,  taking  high  polish;  Rockingham  County,  shaded 
yellowish  gray  and  slate-colored  marble  taking  high  polish.  Only 
the  last  has  been  worked  for  commercial  purposes. 

NORTH   CAROLINA. 

A  narrow  strip  of  marble  is  found  in  Cherokee  County,  N.  C., 
which  is  a  continuation  of  the  beds  in  Fannin  County,  Ga. 

The  stone  is  medium  to  fine  grained  in  texture,  and  of  two 
distinct  colors,  viz.,  a  blue  gray  more  or  less  mottled  and  streaked 
with  white,  and  almost  pure  white. 

The  marble  belt  lies  between  schists  and  quartzites,  and  near 
its  contact  with  these  the  marble  is  apt  to  contain  tremolite, 
talc  and  quartz. 

The  stone  takes  a  good  polish  and  shows  good  contrast  be- 
tween polished  and  hammered  surface. 

In  Swain  County  there  are  beds  of  marble  of  varying  colors, 
from  gray  to  black,  cream  white  and  pink,  various  mixtures, 
and  sometimes  greenish. 


2l8  BUILDING   STONES  AND    CLAY-PRODUCTS 

TENNESSEE. 

The  marbles  of  the  valley  region  of  east  Tennessee  are  well 
known.  They  are  moderately  coarse  grained,  of  variable  color 
and  often  highly  fossiliferous.  The  best-known  variety  is  a 
fossiliferous  dark  chocolate  rock,  variegated  with  white.  Much 
of  the  ornamental  beauty  of  this  stone  is  due  to  the  patterning 
produced  by  the  white  fossils  in  the  rock.  In  addition  to  the 
dark  chocolate  colored  stone,  there  is  a  lighter  colored  gray  and 
pink,  variety  which  is  extensively  used  for  wainscoting. 

All  the  Tennessee  marbles  take  a  good,  durable  polish  and  cut 
to  a  sharp  edge.  They  are  used  for  paneling,  wainscoting, 
furniture  tops,  switchboards,  and,  less  often,  monumental  pur- 
poses. 

GEORGIA. 

The  calcitic  marbles  thus  far  worked  on  a  commercial  scale 
occur  along  the  Louisville  and  Nashville  Railroad  in  the  northern 
part  of  the  state.  The  most  important  deposits  being  found  in 
Pickens  County. 

The  stone  is  coarsely  crystalline  and  often  micaceous.  The 
color  is  white,  white  with  streaks  or  blotches  of  black,  gray  and 
pink  colors.  In  some  the  banding  is  very  pronounced,  and  highly 
ornamental  matched  slabs  are  produced. 

Among  the  varieties  produced,  the  following  may  be  mentioned : 

Cherokee,  white  calcite;  Creole,  black  and  white  mottled, 
coarse  grained,  calcitic;  Etowah,  flesh  colored,  coarse  grained, 
calcitic ;  Southern,  white  with  bluish  gray  markings ;  Silver  Gray 
Cherokee,  bluish  gray. 

The  Georgia  marbles  have,  in  recent  years,  been  extensively 
used  for  constructional  and  monumental  work,  some  splendid 
pieces  of  work  being  seen  at  a  number  of  points.  The  following 
may  be  mentioned  among  others. 

Examples.  —  Minnesota  State  Capitol,  St.  Paul,  Minn.;  Rhode  Island  State 
Capitol,  Providence,  R.  I.;  Carnegie  Public  Library,  Atlanta,  Ga.;  Facade  of  New 
York  Stock  Exchange,  New  York,  N.  Y.;  The  State  Savings  Bank,  Detroit,  Mich.; 
Corcoran  Art  Gallery,  Washington,  D.  C.;  Girard  Trust  and  Banking  Company, 
Philadelphia,  Pa.;  New  Orleans  Court  House,  New  Orleans,  La.;  Royal  Bank  of 
Canada,  Montreal,  Can.;  LaSalle  Street  Station,  Chicago,  111.;  Royal  Insurance 
Building,  San  Francisco,  Cal. 


"^"   '~~^ 

>*  «s 


•s-e 


2IQ 


221 


LIMESTONES  AND   MARBLES  223 

ALABAMA. 

According  to  Smith,  true  marbles  occur  mainly  in  a  narrow 
valley  along  the  western  border  of  metamorphic  rocks,  extending 
from  the  northwestern  part  of  Coosa  County  through  Talladega 
into  Calhoun.  The  best  known  are  in  Talladega  County,  and 
the  principal  quarries  from  which  stone  has  been  obtained  are 
near  Sylacauga  and  Taylor's  mill. 

Some  of  the  marble  is  fine  grained  and  very  white,  closely 
resembling  Carrara  marble;  other  types  are  cream  colored, 
clouded,  or  streaked  with  micaceous  and  talcose  streaks.  The 
last  two  are  undesirable  for  exterior  work. 

Some  of  the  varieties  are  Pocahontas,  Alabama  sunset,  Ala- 
bama iris,  etc. 

Examples.  —  In  rotunda  and  other  parts  of  main  story  of  new  Custom  House, 
also  in  Night  and  Day  Bank,  New  York  City;  National  Metropolitan  Bank, 
Washington,  D.  C.;  exterior  Maryland  Institute,  Baltimore,  Md. 

MISSOURI. 

This  state  does  not  produce  any  true  marble,  but  the  dense, 
light  cream  white  limestone  quarried  near  Carthage  is  often 
classed  as  such  in  the  trade.  This  stone  takes  a  polish  and 
might  be  classed  as  a  monotone  marble. 

Examples. — Denkman  Memorial  Library  at  Rock  Island,  111.;  Court  House, 
Butler,  Mo.;  for  interior  work  of  Masonic  Temple,  Wichita,  Kan. 

COLORADO. 

Marble  deposits  have  been  opened  up  in  recent  years  at  the 
head  of  Yule  Creek,  Gunnison  County.  The  stone  is  fine 
grained,  and  the  following  types  are  said  to  occur:  (i)  White 
statuary  marble,  pure  white,  very  fine  grained,  and  takes  .good 
polish;  (2)  Streaked  black  and  white  with  serpentine  veins;  (3) 
Blue-black,  shading  into  blue-gray  with  blotches  and  veins  of 
green  serpentine;  (4)  Streaked,  dark  mottled,  soft  blue-gray  to 
black  with  a  few  lines  of  jet  black  cut  by  green  veinlets  of  ser- 
pentine; (5)  Pale  flesh,  or  pinkish  chocolate,  mottled  and  gen- 
erally light. 

ARIZONA. 

Some  decorative  marble  has  recently  been  quarried  in  Arizona. 
The  varieties  advertised  are:  Arizona  Opal,  white  with  creamy 


224  BUILDING  STONES  AND   CLAY-PRODUCTS 

yellow  and  pink,  with  light  pink  veins;  Arizona  Pavonazzo, 
strong  creamy  white  and  light  pinkish  tone  with  a  few  strong 
black  veins  ;  Arizona  Pavonazzo,  heavy  veins. 

CALIFORNIA. 

A  dolomitic  marble  is  quarried  north  of  Keeler,  Inyo  County. 
The  stone  is  generally  tine  grained  and  takes  a  good  polish. 
Among  the  varieties  are  a  white,  mottled  white,  gray,  yellow  and 
black.  The  streaked  grayish  black  and  white  has  been  much 
used  for  wainscoting.  The  black  is  used  for  flooring. 


CHAPTER  VI. 
SLATE. 

ON  an  earlier  page  it  was  explained  that  slate  is  a  metamorphic 
rock,  having  a  more  or  less  perfect  cleavage,  because  of  which 
it  has  a  number  of  commercial  uses. 

Slate  is  fine  grained  and  varies  in  color  from  black  or  gray  to 
red,  green  and  purple.  The  lustre  is  usually  dull,  but  some  slate 
is  quite  lustrous. 

Slates  are  derived  by  metamorphism,  chiefly  from  sedimentary 
rock  (shales),  and  the  classification  of  these  is  given  by  Dale  as 
follows : 

(A)  Clay  Slates.     Purple  red  of  Penrhyn,  Wales;    black  of 

Martinsburg,  W.  Va. 

(B)  Mica  Slates. 

(1)  Fading: 

(a)  Carbonaceous  or  graphitic  (blackish). 

Lehigh  and  Northampton  counties,  Pa. ;  Benson,  Vt. 

(b)  Chloritic  (greenish). 

"Sea  green,"  Vermont. 

(c)  Hematitic  and  chloritic  (purplish). 

Purplish  of  Pawlet  and  Poultney,  Vt. 

(2)  Unfading: 

(a)  Graphitic. 

Peachbottom  of  Pa.  and  Md.;  Arvonia,  Va.;  Northfield,  Vt.; 
Brownville,  Monson,  Me.;  North  Blanchard,  Me.;  West 
Monson,  Me. 

(b)  Hematitic  (reddish). 

Granville,  Hampton,  N.  Y.;  Polk  County,  Ark. 

(c)  Chloritic  (greenish). 

"Unfading  green,"  Vermont. 

(d)  Hematitic  and  chloritic  (purplish). 

Purplish  of  Fairhaven,  Vt. ;  Thurston,  Md. 
225 


226  BUILDING   STONES   AND   CLAY-PRODUCTS 

In  the  clay  slates  the  particles  are  merely  compressed  by 
weight  or  pressure  and  cemented  by  carbonates  of  lime  and 
magnesia,  by  clay  and  iron  oxide.  Their  cleavability,  strength 
and  elasticity  are  low. 

The  mica  slates  have  an  abundance  of  mica  scales  developed 
by  metamorphism  and  possess  a  high  grade  of  fissility,  strength 
and  elasticity. 

There  is,  however,  much  variation  in  composition  and  struc- 
ture even  within  this  second  group  —  the  mica  slates.  Thus  the 
amount  of  ferrous  carbonate  determines  the  liability  to  discolor 
on  exposure  to  the  atmosphere,  those  containing  much  being  of 
a  fading  character.  This  gives  us  the  division  of  fading  and 
unfading  slates. 

The  slaty  cleavage  is  an  important  property  which  has  been 
already  referred  to.  As  a  rule,  it  is  not  coincident  with  the 
bedding,  but  may  form  almost  any  angle  with  it. 

Repeated  freezing  and  thawing  has  a  disastrous  effect  on  the 
cleavability  of  slates,  and  the  material  must  be  split  when  fresh 
from  the  quarry. 

Many  slates  show  extremely  fine  plications  on  their  cleavage 
surfaces,  and  to  this  the  name  of  bate  or  false  cleavage  is  given 
by  the  quarrymen. 

The  slip  cleavage  consists  of  minute  plications,  which  result  in 
microscopic  slips  or  faults  along  which  the  slate  breaks  easily. 

Grain  is  a  direction  along  which  the  slate  can  be  split,  but  not 
as  smoothly  as  along  the  true  cleavage.  The  grain  is  indicated 
by  a  somewhat  obscure  striation  on  the  cleavage  surface  in  a 
direction  nearly  parallel  to  the  cleavage  dip. 

Joints  are  found  in  all  slate  quarries  and  may  traverse  the 
slate  in  various  directions.  The  term  Post  is  applied  to  a  mass 
of  slate  traversed  by  so  many  joints  as  to  be  useless.  Ribbons 
are  lines  of  bedding,  or  thin  beds,  which  show  on  the  cleavage 
surface  and  are  often  of  a  different  color.  If  irregular  and 
numerous,  they  may  make  the  slate  worthless,  but  in  many  cases 
do  no  harm. 

Veins  of  quartz  or  calcite  occur  in  some  quarries  and  render 
those  portions  of  the  slate  in  which  they  are  found  worthless. 
Pyrite  in  lumps  or  grains  is  equally  injurious. 


PLATE  XLI,  Fig.  i.     Slate  quarry,  Penrhyn,  Pa.      (Photo  by  H.  Ries.) 


PLATE  XLI,  Fig.  2.  —  Splitting  slate.     (Photo  by  H.  Ries.) 


227 


SLATE  22Q 

The  chemical  analysis  of  slate  is  of  little  value  in  most  cases, 
except  for  purposes  of  scientific  study,  although  those  slates 
which  are  most  likely  to  discolor  seem  to  contain  greater  amounts 
of  ferrous  carbonate. 

PROPERTIES  OF  SLATE. 

The  physical  characters  of  slate  are  mostly  so  different  from 
those  of  other  building  stones  that  a  special  series  of  tests  is 
usually  necessary.  These  properties  and  tests  may  be  referred 
to  separately. 

Sonorousness.  If  a  good-sized  piece  of  roofing  slate  of  the 
usual  thinness  is  suspended  and  struck  with  some  hard  object 
it  will  emit  a  ring  like  semi- vitreous  china.  Mica  slates  are  more 
sonorous  than  clay  slates,  but  those  with  considerable  chlorite 
may  be  deficient  in  this  respect. 

Cleavability.  The  slate  is  split  with  a  thin  chisel  about  two 
inches  wide,  in  order  to  determine  the  smoothness,  thinness  and 
regularity  with  which  it  cleaves. 

Cross  Fracture  (Sculping).  This  property,  which  should  be 
tested  by  an  experienced  person,  is  to  determine  the  character  of 
the  grain. 

Character  of  Cleavage  Surface.  It  should  be  noted  whether 
or  not  the  slate  cleaves  smoothly. 

Lime.  A  drop  of  cold,  dilute  muriatic  acid  applied  to  the 
edges  of  a  freshly  quarried  slate  will,  by  the  effervescence,  indi- 
cate the  presence  of  lime.  Slates  containing  a  large  amount  of 
lime  carbonate  are  more  likely  to  be  acted  upon  by  acids  in  the 
atmosphere. 

Color  and  Discoloration,  The  value  of  a  roofing  slate  depends 
somewhat  upon  its  permanence  of  color.  To  obtain  informa- 
tion on  this  point  the  fresh  slate  should  be  compared  with  pieces 
which  have  lain  on  the  dump  for  several  years,  or  pieces  on  the 
roof. 

Presence  of  Clay.  If  much  is  present,  the  slate  will  emit  an 
argillaceous  odor  when  breathed  upon,  but  the  very  best  slates 
do  not. 


230  BUILDING   STONES  AND   CLAY-PRODUCTS 

Presence  of  Marcasite.  Good  slates  should  be  free  from  this 
form  of  iron  sulphide,  which  is  recognized  by  its  yellowish  color 
and  metallic  lustre.  The  objection  to  it  is  that  it  decomposes 
to  limonite. 

Strength.  The  transverse  strength  of  slate  is  of  importance 
and  should  be  determined.  In  the  best  slates  the  modulus  of 
rupture  should  range  from  7000  to  10,000  pounds.  An  impact 
test  devised  by  Merriman  is  as  follows :  A  wooden  ball  weighing 
15.7  ounces  is  allowed  to  fall  9  inches  upon  a  piece  of  slate  6  by 
7!  inches  and  0.20  to  0.28  inch  thick,  the  blows  being  repeated 
until  the  slate  breaks.  The  foot-pounds  of  work  per  pound  of 
slate  can  be  calculated  from  the  weight  and  thickness  of  the  slate 
and  the  number  of  blows. 

Toughness  or  Elasticity.  If  a  slab  of  slate  is  fastened  between 
two  supports  and  subjected  to  pressure  it  will  bend  slightly 
before  breaking. 

The  deflection  of  certain  Pennsylvania  slates,  when  placed  on 
supports  2 2  inches  apart,  amounts  to  0.27  to  0.313  inch  (Merriman) . 

Density  or  Specific  Gravity.  This  averages  about  2.75,  and  is 
affected  by  the  amount  of  magnetite  or  pyrite  present. 

Abrasive  Resistance.  This  is  of  importance  where  the  slate  is 
used  in  thick  slabs  for  stair  treads.  There  is  no  standard  method 
of  determining  it. 

Corrodibility.  Slates  should  resist  exposure  to  an  acid  atmos- 
phere. They  may  be  exposed  to  it  in  two  ways,  either  by 
moisture  or  rain  water  with  acid  flowing  on  the  upper  surface, 
or  by  the  capillary  creeping  up  of  such  water  between  the  slate 
slabs  on  the  roof. 

A  method  of  testing  this  resistance  consists  in  using  a  solution 
consisting  of  98  parts  of  water,  i  part  of  hydrochloric  acid  and 
i  part  sulphuric  acid.  A  weighed  piece  of  slate  3  by  4  inches 
.was  immersed  in  this  for  120  hours,  then  dried  for  40  hours, 
weighed,  the  solution  strengthened,  and  the  piece  reimmersed 
for  another  120  hours,  and  weighed  again.  The  losses  in  tests 
made  by  Merriman  range  from  o  to  2.76  per  cent. 

Electrical  Resistance.  If  a  slate  is  to  be  used  for  electrical 
switchboards  this  should  be  determined. 


SLATE 


231 


According  to  the  Electrical  Engineers'  Standard  Handbook 
the  resistance  of  slate  runs  about  78,000  megohms  per  centimeter 
cube.  This  is  considerably  higher  than  marble,  which  runs  from 
435  to  510  megohms  per  centimeter  cube.  Slate,  however,  is 
not  as  desirable  as  marble  for  switchboards  for  the  reason  that 
it  is  likely  to  have  veinlets  of  metallic  minerals,  which  sometimes 
cause  a  short  circuiting  of  the  current,  and  it  is  therefore  used 
much  less  now  than  formerly. 

Published  data  of  such  tests  are  rare  even  if  they  have  been 
made. 

Some  tests  of  this  character  have  been  carried  out  on  red  slate 
from  Slatington,  Ark.,  by  Professor  W.  M.  Gladson,1  whose 
description  follows: 

"  These  pieces  of  slate  were  tested  in  comparison  with  three 
pieces  of  gray  slate  taken  at  random  from  old  switch  bases  in 
the  University  electric  laboratory.  A  piece  i  centimeter  cube 


Guard  wire 


Fig.  4.  —  Diagram  showing  electric  connections  made  in  testing  slate. 

was  cut  from  each  sample,  and  these  were  numbered  consecutively 
from  i  to  9,  Nos.  i,  3  and  4,  being  gray  slate.  In  preparing  the 
cubes  metallic  particles  were  found  in  samples  4  and  6,  and  Nos. 
5  and  6  were  so  easily  split  that  it  was  difficult  to  obtain  a  centi- 
meter cube. 

"The  pieces  of  red  slate  as  received  were  smooth  blocks, 
4  by  5  inches  by  f  of  an  inch,  neither  varnished  nor  in  any  way 
filled.  They  were  red  or  reddish-brown,  were  much  softer  than 
the  gray  slate,  and  split  much  more  readily.  All  samples  tested 

1  U.  S.  Geol.  Surv.,  Bull.  430  F,  p.  57. 


232  BUILDING   STONES  AND   CLAY-PRODUCTS 

were  dry  and  appeared  to  be  seasoned.  The  method  of  measur- 
ing the  resistance  of  these  centimeter  cubes  was  as  follows : 

"A  block  of  paraffin  wax  was  attached  to  the  center  of  a  glass 
plate,  which  in  turn  was  thoroughly  insulated  from  the  table  by 
glass  strips  piled  across  one  another.  In  the  top  of  the  paraffin 
block  an  opening  was  cut  i  centimeter  square  and  about  3  milli- 
meters deep.  In  the  bottom  of  the  cavity  thus  formed,  four 
copper  supports  were  embedded  so  that  their  top  surfaces  were 
in  the  same  plane,  about  i  millimeter  below  the  top  of  the  paraffin 
cup.  A  drop  of  mercury  coming  about  flush  with  the  copper 
supports  in  this  cavity  formed  one  terminal  for  making  electric 
connection  to  the  slate  cube.  Contact  with  the  opposite  face 
was  made  by  placing  a  well-amalgamated  zinc  plate  i  centimeter 
square  on  top  of  the  cube.  This  arrangement  insured  equal 
contact  with  each  slate  cube  under  test. 

"The  galvanometer  used  was  of  the  D' Arson val  type,  and  had 
a  working  constant  of  70,533  millimeters  on  the  scale  i  meter 
distant  through  i  megohm  resistance.  The  electromotive  force 
was  furnished  by  storage  cells  and  was  kept  constant  at  42  volts 
during  the  experiment. 

"The  connections  were  made  as  shown  in  the  figure. 

"To  avoid  leakage  over  the  surface  of  the  slate  a  guard  wire 
was  connected  as  shown.  All  readings  were  taken  after  the 
deflections  became  constant;  in  some  cases  they  did  not  become 
so  until  half  an  hour  after  electrification. 

"The  results  of  the  test  are  shown  in  the  following  table, 
from  which  we  find  the  average  resistance  of  all  samples  to  be 
1224.2  megohms  per  cubic  centimeter.  The  average  resistance 
of  the  three  gray  samples  was  1180,  and  of  the  six  red-slate 
samples  1267.8  megohms  per  cubic  centimeter.  Each  piece 
tested,  except  No.  7,  shows  a  different  resistance  between  each 
pair  of  opposite  parallel  faces,  which  seems  to  depend  on  the 
plane  of  cleavage.  The  gray-slate  samples  show  a  decidedly 
higher  resistance  between  faces  of  cubes  perpendicular  to  cleav- 
age planes,  but  in  individual  samples  the  distribution  of  re- 
sistance would  be  greatly  affected  by  the  presence  of  foreign 
conducting  particles  or  seams,  which  are  likely  to  be  present  in 
all  slate." 

The  results  of  these  tests  are  considerably  lower  than  the 
figures  quoted  from  the  Electrical  Engineers'  Standard  Hand- 
book, and  given  on  page  236. 


SLATE 


233 


RESULTS    OF    TESTS    OF    ELECTRIC    RESISTANCE    OF     SLATE 

SAMPLES. 


Sample  number. 

Galvanometer  scale  deflections. 

Resistance.* 

Perpen- 
dicular to 
cleavage 
planes. 

Parallel  to  cleavage 
planes. 

Perpen- 
dicular to 
cleavage 
planes. 

Parallel  to  cleavage 
"  planes. 

D 

D' 

D" 

R 

R' 

R" 

I  
2  

mm. 

39-0 
98.0 
171.0 
35-o 
104.0 

338.9 
91  .0 
57-o 
45-o 

mm. 
40.0 
174.0 
185.0 
94.0 

47-7 
28.0 
91  .0 
51-0 
33-0 

mm. 
44-0 
625.0 
283.0 
43-0 
39-9 
88.0 
48.0 
27.0 
36.0 

Megohms 
1808.5 
719.7 
414.9 
2015.3 
678.2 
208.  1 

775-0 
1500.7 

1567-4 

Megohms 
1763.3 
405.3 
381.2 

750.4 
1476.3 
2519.0 
775-0 
1383  0 
2137-3 

Megohms 
1603.0 
67.I 
249.2 
1640.3 
1767.1 
801.5 
1469.4 
2612.3 
1959-2 

3  

4 

cr 

6  

7  

8  

g  

*  R,  R'  and  R"  correspond  to  the  directions  D,  D'  and  D",  respectively. 
Average  of  Nos.  i,  3  and  4  (gray  slate)  1 180.6  megohms  per  centimeter  cube. 
Average  of  Nos.    2,  5,  6,  7,  8  and  9  (red  slate)   1267.8  megohms  per  centi- 
meter cube. 

Average  of  all  samples,  1224.2  megohms  per  centimeter  cube. 

Tests  of  Slates.  The  following  tables,  taken  from  the  work  of 
Dale  and  Purdue,  include  a  number  of  tests  that  have  been  made 
of  different  kinds  of  slate. 


TESTS  ON  ARKANSAS  SLATE. 


Modulus  of  rup- 
ture, Ibs.  per  sq. 
in 

Modulus  of 
elasticity. 

Specific  gravity. 

Per  cent  absorp- 
tion, 24  hrs. 

Color  and  quarry. 

Max. 

Aver. 

Max. 

Aver. 

Max. 

Aver. 

Max. 

Aver. 

Red;  Southwestern 

Slate  Co  

6,060 

4450 

4,640,000 

3,660,000 

2.86 

2.86 

0.018 

0.017 

Green;    Southwest- 

ern Slate  Co  

6,840 

6620 

6,430,000 

5,980,000 

2.81 

2.81 

0.008 

0.008 

Black;  M.  J.  Har- 

rington   

9,640 

8040 

13,420,000 

11,05)0,000 

2.70 

2.69 

0.016 

0.014 

Reddish      brown; 

M.  W.  Jones.  .  . 

12,590 

9600 

19,530,000 

16,340,000 

2.84 

2.84 

o.oo3 

0.007 

Buff";  C.  B.  Baker. 

4,150 

3720 

6,090,000 

5,100,000 

2.83 

2.82 

0.018 

0.015 

Quoted  from  report  by  Purdue,  Ark.  Geol.  Surv. 


234  BUILDING  STONES  AND   CLAY-PRODUCTS 


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SLATE 


235 


Price  of  Slate.  The  price  of  slate  is  usually  based  on  the 
number  of  slabs  required  to  cover  a  square  (100  square  feet)  laid 
with  3-inch  overlap. 

The  following  figures  taken  from  one  list  give  these  data  for 
Maine  black  slates: 


Number  pieces 
slate  in  a 
square. 

Size. 

Selected, 
No.  i. 

Extra, 
No.  2. 

686 

9X   7 

$4.50 

515 

ioX  8 

5.00 

450 

nX  8 

5.00 

534 

i2X  6 

5.00 

458 

i2X   7 

5-50 

$4.50 

400 

i2X  8 

6.00 

5.00 

356 

i2X  9 

6.00 

5.00 

320 

12X10 

6.00 

5.00 

291 

i4X  9 

7.00 

6.00 

277 

i6X  8 

7-75 

6-75 

185 

16X12 

7-75 

6-75 

192 

18X10 

7-75 

6-75 

170 

20X10 

7-75 

6-75 

127 

22X12 

7.00 

6.00 

iJ5 

24X12 

7.00 

6.00 

In  the  Vermont-New  York  district,  the  price  per  square 
ranges  about  as  follows:  No.  i,  sea  green,  $2.25-14.10;  Inter- 
mediate, sea  green,  $3.00-13.25;  No.  i,  variegated  purple,  $2.75- 
$4.10;  No.  i,  unfading  green,  $4.oo-$5.25. 


Fig.  5.  —  Diagram  showing  some  patterns  of  slate  that  can  be  cut  on  a  machine. 


236 


BUILDING   STONES  AND   CLAY-PRODUCTS 


The  figures  given  for  Penrhyn,  N.  Y.,  purple  are  somewhat 
as  below: 


Superficial  measure. 


i-  4  square  feet 

4-  8  square  feet 

8-i2  square  feet 

12-15  square  feet 

20-25  square  feet 

30-35  square  feet 


Thickness. 


I  inch  or 
less. 

i|  inches. 

1  5  inches. 

2  inches. 

$0.28 

$0.32 

$0.36 

$0.44 

0.32 

0.36 

0.40 

0.48 

0.36 

0.40 

0.44 

0.52 

0.42 

0.46 

0.50 

0.58 

0-54 

0.58 

0.62 

0.70 

0.66 

0.70 

0.74 

0.82 

Rubbing,  notching,  grooving,  etc.,  are  charged  extra. 


Finishers. 


START LN.Q  AND  FINJSHIN& 
Fig.  6.  —  Diagram  showing  section  of  slate  roof  with  starting  and  finishing 


Quarrying.  The  waste  in  slate  quarrying  is  very  high,  prob- 
ably never  under  60  per  cent,  and  not  infrequently  as  much  as 
80  per  cent.  The  utilization  of  the  tremendous  waste  heaps  is 
an  unsolved  problem. 

The  salable  material  taken  from  the  quarry  may  be  used  either 
for  roofing  purposes  or  millstock.  The  latter  represents  a  more 
massive  type,  which  is  cut  into  slabs  for  tubs,  sinks,  table  tops, 
switchboards,  blackboards,  etc. 

Distribution  of  Slate  in  the  United  States.  Most  of  the  do- 
mestic slate  production  comes  from  the  eastern  states,  the 
quarrying  districts  forming  a  broken  belt  extending  from  Maine 
to  Georgia.  Outside  of  this  there  are  very  few  developed  areas, 


SLATE  237 

these  being  in  Arkansas  and  California.     The  several  occur- 
rences are  briefly  described  below. 

MAINE. 

The  chief  slate  area  is  located  in  the  central  portion  of  the 
state  and  important  developments  occur  around  Monson  and 
West  Monson,  etc.  That  quarried  at  Monson  is  a  dark  gray 
color,  and  the  slate  obtained  at  the  other  localities  is  similar. 
The  product  of  the  region  is  used  chiefly  for  roofing  purposes, 
although  some  quarries  turn  out  mills tock  as  well. 

VERMONT. 

The  most  important  district  lies  in  Rutland  and  Bennington 
counties,  and  supplies  the  well-known  green  and  purple  slate. 
This  belt  passes  south  westward  into  Washington  County,  N.  Y., 
but  the  quarries  there  are  of  less  importance. 

The  following  varieties  are  obtained: 

Sea  Green  Slate.  When  freshly  quarried  this  varies  from  light 
gray  to  a  slightly  greenish  gray.  The  texture  is  usually  fine, 
and  the  slate  is  sometimes  slightly  magnetitic ;  it  also  effervesces 
slightly.  After  exposure  for  a  few  years  it  changes  to  brownish 
gray,  but  since  the  different  beds  discolor  unevenly,  the  roof  may 
assume  a  mottled  appearance.  The  slate  is  used  exclusively  for 
roofing  purposes. 

Unfading  Green  Slate.  This  is  of  greenish  gray  color,  fine 
texture,  and  roughish,  lustreless  cleavage  surface.  It  is  mag- 
netitic, and  does  not  effervesce  with  cold  acid. 

Several  years'  exposure  produces  scarcely  any  perceptible 
change.  The  fissility  is  inferior  to  the  sea  green.  The  slate  is 
used  largely  for  roofing  purposes. 

In  the  northern  and  western  part  of  the  green  slate  belt, 
those  beds  having  perfect  cleavage  are  used  as  millstock  and 
utilized  for  switchboards  and  billiard- table  tops. 

Purple  and  Variegated.  The  purple  is  described  as  being  dark 
purplish  brown;  the  variegated  is  like  the  sea  green  and  the 
unfading  green,  but  spotted  with  purplish  brown.  They  are 
found  interbedded  with  both  the  sea  green  and  unfading  green, 
and  correspond  with  them  in  texture  and  lustre. 


238  BUILDING  STONES  AND   CLAY-PRODUCTS 

The  purple  of  the  variegated  is  said  to  discolor  less  than  the 
sea  green. 

NEW  YORK. 

Washington  County,  N.  Y.,  contains  a  number  of  slate  quar- 
ries, the  area  being  a  continuation  of  that  in  Rutland  County, 
Vermont. 

The  most  important  types  quarried  are  the  red  and  green 
slates,  obtained  near  Granville,  Whitehall  and  Hampton. 

The  red  slate  is  a  reddish  brown,  and  becomes  brighter  on 
exposure.  It  is  fine  grained  and  non-fading. 

The  bright  greenish  slate  is  interbedded  with  the  former  or 
sometimes  grades  into  it  along  the  strike.  It  is  likewise  unfading. 
Both  effervesce  slightly  with  acid. 

NEW  JERSEY. 

The  New  Jersey  quarries  are  mostly  in  a  slate  of  character 
corresponding  to  the  southeasterly  or  "hard  vein"  slates  of  the 
region  about  Chapmans,  Pa. 

In  this  stone  both  the  slate  and  ribbons  are  harder  than  those 
of  the  soft  vein  or  northwesterly  areas,  like  the  Lehigh,  Pen  Argyl 
and  Bangor,  Pa.,  regions. 

That  quarried  at  Newton,  N.  J.,  is  a  hard,  bluish  black  stone. 

PENNSYLVANIA. 

Aside  from  the  Peach  Bottom  slate  referred  to  under  Mary- 
land, an  important  area  is  found  in  Northampton  and  Lehigh 
counties  of  eastern  Pennsylvania,  and  forms  a  large  source  of 
supply,  the  two  chief  centers  being  Bangor  and  Slatington. 

In  the  broad  strip  there  are  two  belts  of  commercial  slate. 
The  more  northern  of  the  two  is  known  as  the  soft  vein,  and 
consists  of  belts  of  relatively  soft  slate,  which  is  thick  enough 
between  the  ribbons  to  furnish  large  slabs  for  millstock  or  roofing 
slate. 

The  more  southern  belt  or  hard  vein,  consists  of  small  beds  of 
harder  slate,  separated  by  small  ribbons  not  coarse  enough  to 
interfere  with  their  use  either  as  millstock  or  roofing  slate. 


i 


SLATE  241 

The  quarries  at  Bangor,  East  Bangor,  Pen  Argyl,  Daniels- 
ville,  Slatington  and  Slatedale  are  in  the  soft  vein,  while  Belfast 
and  Chapman  are  in  the  hard  vein. 

The  slates  of  eastern  Pennsylvania  are  mostly  a  very  dark 
bluish  gray,  or  grayish  black.  They  are  used  chiefly  for  roofing 
purposes,  but  some  of  the  quarries  produce  considerable  millstock. 

MARYLAND. 

An  important  slate-producing  district  known  as  the  Peach 
Bottom  slate  area  lies  on  the  border  of  Maryland  and  Pennsyl- 
vania, but  the  chief  production  comes  from  the  former  state,  the 
quarries  being  located  near  Cardiff. 

The  slate  is  said  to  be  tough,  fine  grained  and  moderately 
smooth  in  texture.  It  is  also  less  fissile  than  many  of  the  slates 
quarried  to  the  northeast  and,  according  to  Merrill,  will  yield,  as 
a  rule,  only  six  slabs  to  the  inch,  while  those  of  Monson,  Me., 
and  Slatington,  Pa.,  yield  twice  that  number.  Its  greater 
strength  and  elasticity  are  thought  to  be  due  to  the  fact  that 
it  is  more  metamorphosed  than  most  slates.  The  color  is  good 
and  the  weathering  qualities  are  regarded  as  excellent. 

WEST  VIRGINIA. 

A  black  slate  of  slightly  brownish  hue,  lustreless  character 
and  roughish  cleavage  is  quarried  at  Martinsburg. 

VIRGINIA. 

A  dark  gray  slate,  which  is  of  durable  color  and  good 
strength,  is  produced  at  Arvonia. 

GEORGIA. 

Roofing  slate  is  quarried  near  the  town  of  Rockmart.  It  is 
black  in  color  and  splits  readily  into  slabs  of  moderate  thickness. 

ARKANSAS. 

Slate  deposits  are  known  in  west  central  Arkansas,  in  a  belt 
about  100  miles  long  lying  west  of  Little  Rock.  During  recent 
years  the  best  developments  have  been  in  Polk  and  Montgomery 
counties. 


242  BUILDING  STONES  AND   CLAY-PRODUCTS 

The  following  grades  are  noted:  (i)  Black  slate  from  Mena; 
(2)  Dark  reddish  slate,  somewhat  darker  than  the  New  York  red 
slate;  (3)  Reddish  slate;  (4)  Greenish  gray  slate,  resembling  the 
sea  green  of  Vermont;  (5)  Light  greenish  slate;  (6)  Dark  and 
light  gray  slate. 

The  slate  has  been  quarried  for  roofing  purposes  and  switch- 
boards, but  does  not  seem  altogether  satisfactory  for  the  first, 
on  account  of  a  tendency  to  disintegrate. 

CALIFORNIA. 

One  important  slate  area  is  known  in  the  state  in  Eldorado 
County.  The  material  is  a  dense,  deep  black  slate,  which  splits 
finely  and  regularly,  with  a  smooth,  glistening  surface.  It  makes 
good  roofing  material,  but  the  frequency  of  the  ribbons  and 
pyrite  nodules  interferes  with  its  use  as  millstock. 

The  California  slates  are  of  considerable  commercial  impor- 
tance, as  they  are  the  sole  source  of  supply  on  the  Pacific  Coast. 
They  are  also  of  interest  scientifically,  because  they  have  been 
derived  by  the  metamorphism  of  igneous  rocks  instead  of  the 
usual  sedimentary  ones. 


CHAPTER  VII. 
SERPENTINE. 

PURE  serpentine  is  a  hydrous  silicate  of  magnesia,  but  masses 
of  serpentine  rock  are  rarely  pure  and  usually  contain  varying 
quantities  of  such  impurities  as  iron  oxides,  pyrite,  hornblende, 
pyroxene  and  carbonates  of  lime  and  magnesia. 

Many  serpentines  are  green  or  greenish  yellow,  while  others, 
especially  the  more  impure  ones,  are  various  shades  of  black,  red 
or  brown. 

Spotted  green  and  white  varieties  are  called  ophiolite  or  ophi- 
calcite.  In  these  the  white  ground  is  calcite,  while  the  green 
spots  are  serpentine,  which  may  contain  a  core  of  some  other 
silicate  mineral. 

Verde  antique  is  a  somewhat  general  name  applied  to  green 
serpentinous  marbles. 

Serpentine  sometimes  occurs  in  sufficiently  massive  character 
to  be  used  in  structural  or  decorative  work,  but  owing  to  the 
frequent  and  irregular  joints  found  in  nearly  all  serpentine 
quarries  it  is  difficult  to  obtain  any  slabs  except  small  ones. 

As  a  general  rule  it  is  extremely  unsafe  to  use  serpentine  for 
exterior  work  in  a  severe  climate,  but  for  interior  decoration 
its  softness,  beautiful  color,  and  high  polish  make  it  a  very 
desirable  stone. 

The  objection  to  it  for  exterior  application  is  that  it  weathers 
irregularly,  cracks,  loses  its  lustre  and  fades  in  spots.  Indeed, 
it  is  one  of  the  most  defective  stones  to  use  outdoors. 

Distribution  of  Serpentine  in  the  United  States.  There  are 
comparatively  few  occurrences  of  this  rock  in  suitable  quantities 
for  quarrying,  moreover  only  a  small  number  of  these  are 
worked,  and  even  then  not  continuously.  Only  the  more  im- 
portant ones  are  mentioned. 

243 


244  BUILDING  STONES  AND   CLAY-PRODUCTS 

Massachusetts.  Some  serpentine  has  been  quarried  in  the 
Hoosac  Mountain  Range.  According  to  Crosby  (quoted  by 
Merrill),  the  quarry  affords  dark  green  serpentine,  serpentinized 
gray  marble  and  massive,  spangled  serpentinized  marble. 
Little  use  appears  to  have  been  made  of  this  stone. 

Vermont.  Near  Roxbury  there  is  found  a  serpentine  which 
G.  P.  Merrill  has  characterized  as  "one  of  the  most  beautiful  of 
all  our  serpentines  and  the  best  adapted  for  all  kinds  of  interior 
decorative  work.  The  colors  are  deep,  bright  green,  traversed 
by  a  coarse  network  of  white  veins."  The  stone  also  takes  a 
beautiful  polish. 

New  York.  Attempts  have  been  made  to  quarry  an  ophi- 
calcite  found  near  Moriah  and  Port  Henry  in  Essex  County, 
N.  Y.  The  stone  is  rather  decorative  and  takes  a  good  polish, 
but  the  reasons  which  have  apparently  prevented  its  extended 
use  are  difficulty  of  obtaining  large  blocks  and  presence  of  pyrite. 

New  Jersey.  Serpentine  for  decorative  work  has  been  quarried 
north  of  Phillipsburg  on  the  Delaware  River.  The  stone  is  of 
a  dark  green  color,  and  also  shows  a  mottled  mixture  of  dark 
and  light,  occasionally  sprinkled  with  grayish,  pinkish  or  flesh- 
colored  dolomite  crystals,  and  sometimes  veined  with  streaks 
or  seams  of  pure  white  compact  to  fibrous  calcite,  in  which  are 
embedded  fibers  of  asbestos.  Much  of  this  rock  furnishes  beau- 
tiful polished  slabs. 

Pennsylvania.  A  handsome  ornamental  serpentine,  known  as 
verdolite,  has  been  quarried  near  Easton,  but  while  the  stone 
is  very  beautiful  the  blocks  are  of  very  irregular  size. 

This  serpentine  has  been  used  recently  for  interior  work  in 
the  Episcopal  Cathedral  of  St.  John  the  Divine  in  New  York 
City.  The  parts  are  the  floor  border  (in  part)  in  the  choir ;  choir 
steps;  ambulatory;  bands  and  moldings  in  the  interior. 

Several  serpentine  areas  are  found  in  southeastern  Pennsyl- 
vania, but  none  are  suitable  for  monumental  work.  Quarries 
have  been  operated  in  the  town  of  West  Chester,  Chester  County, 
and  have  in  the  past  supplied  not  a  little  stone  for  building 
purposes.  It  has  been  used  for  some  of  the  University  of 
Pennsylvania  buildings  and  some  Philadelphia  churches. 


PLATE  XLIII.  —  Serpentine  Pedestal,  Charlottesville,  Va.     This  stone  has  been 

attacked  to  an  appreciable  extent  by  the  weathering  agents. 

(Photo  by  H.  Ries.) 


245 


PLATE  XLIV.  —  Serpentine  from  Roxbury,  Vt. 


247 


ONYX    MARBLES  249 

Maryland.  Serpentine  has  been  quarried  sporadically  in  this 
state  for  a  number  of  years,  and  the  quarries  on  Broad  Creek  in 
eastern  Hartford  County  have  supplied  some  good  stone.  The 
stone  is  compact,  of  dark  green  color,  and  polishes  well.  It 
makes  an  excellent  decorative  stone  for  interior  work  but  has 
been  little  used. 

Georgia.  A  handsome  serpentine  has  been  worked  at  the 
Verde  Antique  Marble  quarry  near  Holly  Springs,  Cherokee 
County. 

The  stone  is  described  as  massive,  with  a  slight  tendency 
towards  schistosity,  but  is  not  uniform  in  structure  or  mineral 
composition.  It  shows  beautiful  venations.  The  stone  has 
not  been  quarried  steadily  and  is  adapted  to  interior  work. 

Examples.  —  Corridors  of  Prudential  Building  and  Smoking  Room  at  Terminal 
Station,  Atlanta,  Ga. 

California.  Serpentine  is  not  an  uncommon  rock  in  this  state, 
but  the  production  for  structural  and  decorative  work  is  almost 
negligible.  The  main  supply  seems  to  have  come  from  quarries 
sixteen  miles  northeast  of  Victor  ville.  It  varies  from  light  yellow- 
green  to  dark  green,  and  is  said  to  have  been  used  for  interior 
decoration  in  Los  Angeles  and  San  Francisco. 

Washington.  Serpentine  has  been  quarried  in  Stevens  County, 
where  it  is  associated  with  marble.  It  is  of  different  shades  of 
green,  with  white  carbonate  minerals  scattered  through  it.  The 
types  quarried  include  Royal  Washington,  Landscape  Green, 
and  Athenian  Green. 

ONYX  MARBLES. 

The  term  onyx  marble  is  applied  to  two  types  of  calcareous 
rock  having  a  crystalline  texture. 

One  of  these  is  a  chemical  deposit  formed  in  limestone  caverns. 
As  surface  waters  seep  through  limestones  they  take  some  lime 
carbonate  in  solution,  which  they  deposit  later  on  the  roof  or 
floor  of  the  caverns  into  which  they  find  their  way. 

The  other  type  of  onyx  marble  is  a  travertine  or  hot-spring 
deposit,  precipitated  on  the  surface. 

In  both  cases  the  lime  carbonate  precipitated  from  the  water 
is  built  up,  layer  upon  layer,  but  the  deposits  are  rarely  of  great 


250  BUILDING  STONES  AND   CLAY-PRODUCTS 

thickness,  and  far  less  extensive  than  those  of  the  ordinary  lime- 
stones and  marbles. 

Onyx  marbles  usually  show  a  characteristic  banding,  which 
is  due  to  their  mode  of  accumulation,  and  while  successive 
layers  may  vary  slightly  in  their  color  and  texture,  still  in  good 
stones  there  is  little  tendency  for  the  rock  to  separate  along 
these  planes. 

The  decorative  beauty  of  the  stone  is  due  to  its  translucency, 
to  the  cloudings  produced  chiefly  by  iron  oxide,  and  to  the  fine 
veins  which  extend  through  the  rock  in  different  directions. 

These  veins  are  sometimes  emphasized  by  the  addition  of 
coloring  matter  which  has  filtered  in  along  the  fractures  in  the 
rock. 

The  colorings  shown  by  onyx  marbles  include  different  shades 
of  green,  red-brown,  red,  yellow  and  amber. 

The  cave  onyx  is  usually  less  translucent  and  coarser  grained 
than  the  travertine  onyx. 

There  are  comparatively  few  localities  which  supply  onyx 
marbles  of  commercial  value. 

Deposits  are  known  to  occur  in  Arizona  and  California,  but 
they  have  been  worked  only  to  a  very  small  extent,  although 
some  of  them  possess  considerable  beauty. 

One  of  the  main  sources  of  supply  has  been  the  region  south- 
east of  Pueblo,  Mexico,  but  the  quarries  are  small,  there  is  much 
waste  in  quarrying  and  it  is  difficult  to  obtain  large  slabs. 

Highly  ornamental  onyx  of  white,  rose,  red,  yellow  and  green 
colors  is  obtained  from  Algeria. 

Persia,  Italy,  France,  Egypt  and  Argentina  have  all  supplied 
some  handsome  stone  of  this  class. 

Onyx  marbles  are  quite  frequently  used  for  wainscoting  and 
paneling,  as  well  as  for  table  tops  and  counters.  Some  are  also 
employed  for  ornamental  purposes. 

When  used  in  slab  form,  little  attention  is  paid  to  matching 
the  patterns  of  the  different  slabs. 

In  rare  cases  onyx  marbles  are  set  as  floor  tiling  and  stair 
treads,  but  this  is  a  serious  error,  as  the  stone  is  not  sufficiently 
strong  or  durable  for  this  purpose. 


PART   II. 
CLAY  PRODUCTS. 


251 


CHAPTER  VIII. 
PROPERTIES   OF  CLAY.1 

THE  clay  products  in  which  the  architect  is  especially  inter- 
ested are  those  which  are  used  chiefly  for  structural  and  decora- 
tive work. 

This,  then,  would  include  building  brick,  either  common  or 
front,  enameled  brick,  fireproofing,  architectural  terra-cotta, 
wall,  floor  and  roofing  tiles,  sewer-pipe  and  sanitary  ware. 

As  regards  the  finished  product,  the  architect  should  not  only 
have  some  knowledge  of  the  qualities  and  applications  of  the 
ware  itself,  but  it  is  also  important  that  he  should  possess  some 
information  regarding  the  raw  materials  employed  and  the 
method  of  manufacture,  since  these  more  or  less  directly  affect 
the  character  of  the  finished  article. 

Before  taking  up  the  different  classes  of  burned  clay  wares, 
it  may  be  desirable,  therefore,  to  give  a  brief  discussion  of  the 
raw  materials  widely  employed  in  their  production. 

The  properties  of  clay  may  be  divided  into  two  groups,  physical 
and  chemical,  the  former  being  the  more  important.  They  de- 
termine to  a  large  extent  the  use  to  which  the  clay  can  be  put, 
and  may  even,  in  some  cases,  influence  the  behavior  of  the  clay 
in  manufacturing,  as  well  as  the  character  of  the  finished  product. 

PHYSICAL  PROPERTIES. 

These  include,  among  others,  plasticity,  air  and  fire  shrink- 
age, tensile  strength,  and  fusibility. 

Plasticity.  This  may  be  defined  as  the  property  which  clay 
possesses  of  forming  a  plastic  mass  when  mixed  with  water,  thus 
permitting  it  to  be  molded  into  any  desired  shape,  which  it 
retains  when  dry.  It  is  an  exceedingly  important  property,  the 

1  For  a  more  detailed  discussion  of  this  subject  see  Ries, "  Clays,  their  Occurrence, 
Properties  and  Uses,"  Wiley  and  Sons. 

253 


254  BUILDING  STONES  AND   CLAY-PRODUCTS 

more  so  if  the  clay  is  to  be  modeled  into  complex  designs,  such 
as  are  often  called  for  in  the  production  of  terra-cotta  wares. 
Clays  vary  from  exceedingly  plastic  or  "  fat  "  ones  to  those  of 
low  plasticity,  which  are  termed  lean.  In  order  to  get  a  mass 
of  the  proper  plasticity  the  manufacturer  often  mixes  two  clays 
of  different  character.  Highly  plastic  clays  often  show  a  high 
shrinkage,  while  in  lean  ones  the  reverse  is  usually  true.  The 
clay  worker,  therefore,  sometimes  adds  sand  to  the  clay,  in  order 
to  reduce  the  shrinkage  and  sometimes  also  the  plasticity.  If 
too  much  sand  is  added  it  may  make  the  product  porous  and 
weak,  especially  if  it  is  not  hard  burned.  An  excellent  example 
of  this  is  often  seen  at  some  small  brick  yards,  where  the  brick- 
maker  either  uses  a  clay  that  is  very  sandy,  or  else  adds  too  much 
sand  to  a  plastic  one.  One  result  of  this  is  that  it  makes  the  clay 
work  more  easily,  but  yields  an  open,  soft  brick. 

Shrinkage.  Two  kinds  of  shrinkage  are  recognized,  i.e.,  air 
shrinkage  and  fire  shrinkage.  The  former  takes  place  while  the 
clay  is  drying  after  being  molded,  the  latter  occurs  during  firing. 
Both  are  variable,  and  while  a  small  amount  at  least  is  desirable, 
in  order  to  permit  the  clay  particles  to  draw  together  to  a  tight 
body,  an  excess  may  lead  to  serious  results.  Excessive  air  or 
fire  shrinkage  often  causes  cracking  or  warping  of  the  clay  during 
drying  and  burning  respectively,  and  is  to  be  avoided. 

The  clay  worker  should  therefore  adjust  his  mixture  so  as  to 
have  the  proper  amount  of  shrinkage,  and  where  the  finished 
ware  must  have  certain  dimensions  this  is  often  adjusted  with 
considerable  care. 

A  word  more  should  be  said  about  the  fire  shrinkage.  This 
usually  begins  during  the  burning  process  at  a  temperature  of 
redness  and  increases  with  the  temperature  of  burning  up  to  a 
point  at  which  the  clay  is  vitrified,  beyond  which  the  material 
swells.  The  fire  shrinkage  does  not  proceed  at  the  same  rate 
in  all  clays,  nor  do  they  all  reach  their  maximum  shrinkage  at  the 
same  heat.  Moreover,  some  clays,  notably  the  sandy  and  cal- 
careous ones,  may  even  expand  slightly  at  a  dull  red  heat. 

In  the  manufacture  of  most  clay  products  an  average  total 
shrinkage  of  about  eight  or  nine  per  cent  is  commonly  desired. 


PROPERTIES   OF   CLAY  255 

Tensile  Strength.  Tensile  strength  is  the  resistance  which  a 
mass  of  air-dried  clay  offers  to  rupture.  It  is  regarded  by  many 
as  an  important  property  and  helps  the  clay  to  withstand  the 
shocks  of  handling  in  its  air-dried  condition.  It  bears  no  neces- 
sary relation  to  the  strength  of  the  burned  ware. 

The  transverse  strength  of  the  air-dried  clay  stands  in  direct 
relation  to  the  tensile  strength. 

Fusibility.  This  is  one  of  the  most  important  properties,  of 
clay.  When  subjected  to  a  rising  temperature,  clays,  unlike 
metals,  soften  slowly,  and  hence  fusion  takes  place  gradually. 
In  fusing,  the  clay  passes  through  three  stages,  termed  respec- 
tively, incipient  fusion,  vitrification  and  viscosity.  It  is 
somewhat  difficult  at  times  to  exactly  locate  each  of  these,  so 
gradual  is  the  change,  but  the  recognition  of  them  is  of  consider- 
able practical  importance.  They  might  be  defined  somewhat 
as  follows :  - 

Incipient  fusion  is  the  point  at  which  the  clay  grains  or  cement 
have  become  sufficiently  soft,  in  part  at  least,  to  make  the  mass 
stick  together.  The  clay  body  is  still  very  porous  and  can  be 
scratched  with  a  knife.  It  is  not,  therefore,  "  steel  hard." 

Vitrification  represents  a  degree  of  heating  sufficient  to  soften 
the  grains  so  that  extensive  fluxing  has  taken  place,  and  the 
particles  have  settled  together,  forming  a  tight,  solid,  practi- 
cally non- absorbent  mass.  The  clay  body  still  holds  its  shape, 
however. 

Viscosity  is  the  stage  at  which  a  clay  has  become  sufficiently 
heated  to  so  soften  that  it  no  longer  holds  its  shape. 

Comparison  of  different  clays  shows  us: 

(i)  That  the  temperature  of  incipient  fusion  is  not  the  same 
in  all,  and  (2)  That  the  three  stages  are  not  equi-spaced. 

Thus  in  calcareous  clays  the  temperature  interval  between  the 
extreme  points  (incipient  fusion  and  viscosity)  is  very  small, 
while  in  other  clays  it  may  be  quite  large. 

The  practical  bearing  of  these  facts  is  this:  In  burning  a 
kiln  full  of  ware,  it  is  impossible  to  control  the  temperature 
within  a  few  degrees,  so  that  if  the  ware  is  to  be  vitrified,  we 
must  have  a  sufficiently  large  temperature  interval  between 


256  BUILDING   STONES  AND   CLAY-PRODUCTS 

vitrification  and  viscosity,  to  permit  reaching  the  former  point 
without  danger  of  running  on  to  the  latter,  and  melting  down 
the  entire  contents  of  the  kiln. 

The  degree  of  vitrification  is  indicated  by  the  absorption. 
Common  brick,  which  are  usually  burned  to  incipient  fusion  or  a 
little  beyond,  show  an  absorption  of  from  ten  to  twenty-five 
per  cent,  while  paving  brick,  which  are  vitrified  or  nearly  so, 
have  from  one  to  five  or  six  per  cent  absorption. 

CHEMICAL  PROPERTIES. 

The  chemical  composition  of  a  clay  influences  the  color  in 
burning  and  the  fusibility,  but  is  not  the  only  factor  affecting 
these  results ;  for  this  reason  the  use  of  the  chemical  analysis  for 
purposes  of  interpretation  is  somewhat  restricted. 

The  substances  usually  determined  in  the  chemical  analysis  are 
silica  (Si02),  alumina  (A12O3),  ferric  oxide  (Fe2O3),  lime  (CaO), 
magnesia  (MgO),  alkalies  (Na2O,K20)  and  water  of  combination 
(H2O).  Others  which  are  rarely  determined  are  carbon  (C), 
sulphur  trioxide  (SOs)  and  carbon  dioxide  (CO2). 

The  effects  of  these  are  somewhat  as  follows:  Iron  oxide  if 
evenly  distributed  tends  to  color  the  clay  some  shade  of  red, 
brown  or  buff  under  normal  conditions  of  burning.  Thus  a 
clay  free  from  iron  oxide  usually  burns  white,  one  with  a  small 
percentage  burns  buff  and  one  with  considerable  iron  oxide 
burns  red  or  brown. 

Lime,  if  evenly  distributed  through  the  clay  and  present  in 
great  excess  over  the  iron  oxide,  counteracts  it  and  gives  a  buff 
or  cream  coloration,  unless  the  ware  is  underburned.  The  well- 
known  Milwaukee  cream  brick  are  an  example  of  this.  The 
Philadelphia  red  brick,  so  much  in  fashion  in  former  years,  owe 
their  color  to  a  liberal  quantity  of  iron  oxide  in  the  clay.  Brick 
manufacturers  sometimes  improve  the  color  of  soft-mud  brick 
by  adding  some  hematite  (iron  oxide)  to  the  molding  sand. 

If  present  in  lumps  the  lime  may  slake  and  split  the  brick 
(Plate  XLIX,  Fig.  i).  For  this  reason  any  lime  pebbles  in  the 
clay  should  either  be  eliminated  or  rendered  harmless  by  crush- 
ing, since  in  the  burning  of  the  brick  they  are  converted  into 


PROPERTIES    OF    CLAY  257 

quicklime.  An  attempt  is  sometimes  made  to  prevent  the 
trouble  by  quenching  the  bricks  with  water  when  they  are 
taken  from  the  kiln. 

Iron  oxide,  lime,  magnesia  and  alkalies  are  spoken  of  collec- 
tively as  fluxes  and  lower  the  fusibility  of  the  clay,  so  that,  other 
things  being  equal,  one  with  a  high  total  percentage  of  these  will 
fuse  at  a  lower  temperature  than  one  containing  a  small  quantity, 
provided  the  fluxes  are  evenly  distributed  through  the  clay  and 
the  latter  is  fine  grained. 

Most  brick  clays  burn  red  because  of  the  iron  oxide  which  they 
contain,  and  also  fuse  at  a  comparatively  low  heat,  while  fire  clays 
burn  buff  because  of  their  low  iron  contents,  and  also  withstand  a 
high  degree  of  heat,  on  account  of  their  low  percentage  of  fluxes. 

We  see  then  that  a  buff  or  cream  brick  can  be  made 
either  from  a  very  calcareous  clay,  or  from  one  which  is  low 
in  both  lime  and  iron  oxide. 

The  effect  of  carbon  is  this:  Carbon,  in  order  to  burn,  requires 
oxygen.  This  it  may  obtain  from  the  kiln  atmosphere,  or,  failing 
this,  from  ferric  oxide  present  in  the  clay,  as  a  result  of  which  the 
ferric  oxide  becomes  reduced  to  ferrous  oxide.  The  latter,  how- 
ever, combines  readily  with  the  silica  in  the  clay,  forming  an 
easily  fusible  ferrous  silicate.  Now,  as  a  result  of  this  fusion, 
which  begins  first  in  the  outer  portion  of  the  brick,  a  tight,  vitri- 
fied zone  forms  around  the  center  which  still  contains  the  carbon. 
The  carbon  in  this  inner  zone  may  continue  to  burn  and  liberate 
gases,  which,  being  unable  to  escape  through  the  outer  fused 
zone,  exert  sufficient  pressure  to  bloat  the  brick.  Or,  in  any 
event,  if  burning  does  not  go  far  enough  to  cause  bloating,  there 
may  be  a  black  core. 

Sulphur  is  present  in  many  clays,  commonly  in  the  form  of 
pyrite,  a  sulphide  of  iron,  whose  yellow  metallic  grains  and 
lumps  are  often  easily  noticed. 

In  -burning,  the  sulphur  is  driven  off  in  gaseous  form,  as  sul- 
phurous or  sulphuric  acid  gas,  but  does  not  pass  off  until  after 
the  chemically  combined  water  and  carbon.  If  allowed  to  re- 
main in  the  clay  it  is  a  common  cause  of  premature  swelling  and 
black  coring. 


258 


BUILDING   STONES  AND   CLAY-PRODUCTS 


Analyses  of  Clay.  The  following  table  will  serve  to  show  the 
variation  in  composition  of  clay.  For  purposes  of  manufacture 
these  are  of  comparatively  little  value,  as  they  throw  little  light 
on  the  physical  behavior  of  the  material.  The  interpretations 
which  can  be  made  from  these  are  to  be  regarded  as  of  only 
approximate  character. 

ANALYSES  SHOWING  VARIATION  IN  COMPOSITION  OF  CLAYS. 


I. 

II. 

III. 

IV. 

V. 

VI. 

Silica  (SiOa) 

AC     70 

<6    2 

66  01 

88  71 

<Q    O3 

47   02 

Alumina  (A12O3)  

4O.6l 

2^  .  7 

18.82 

4  88 

II     19 

14  40 

Ferric  Oxide  (Fe2O3)  
Lime  (CaO) 

i-39 

O    AC, 

i-S 
o  6 

6-33 

O    Z< 

2.00 

o  30 

2.77 
12    l6 

3.60 
1  2    30 

Magnesia  (MgO) 

O    OQ 

I    c 

i  88 

O  07 

o  80 

08 

Soda  (Na2O)  . 

2     2 

o  08 

tr. 

o  18 

CO 

Potash  (K2O)  
Titanic  acid  (TiO2)  
Water  (H2O)  

2.82 
8.98 

i-4 

I  .0 

II  .  I 

.16 

o-95 
4.80 

tr. 
0.90 

2.28 

tr. 
i-05 

2.  IO 

.  20 
.  22 
.85 

Carbon  dioxide  (CO2) 

o  60 

CO 

Sulphur  trioxide  (SO3) 

44 

Organic  matter.  .  . 

34 

Moisture  

•35 

Total  

100.39 

99.8 

99.58 

100.04 

98.88 

100.35 

I.   A  white  burning  clay. 
II.   Buff  burning  fire  clay. 

III.  Red  burning  brick  clay. 

IV.  Sandy  brick  clay. 

V.    Calcareous,  buff  burning  brick  clay. 
VI.   A  red  burning  shale.     Develops  black  core  if  burned  too  fast. 


CHAPTER  IX. 
BUILDING   BRICKS. 

Kinds  of  Brick.  Under  this  heading  are  included  common 
brick,  face  or  pressed  brick,  enameled  brick  and  glazed  brick. 

Common  brick  include  all  those  used  for  ordinary  structural 
work  and  are  employed  usually  for  side  and  rear  walls  of  build- 
ings or,  indeed,  for  any  portion  of  the  structure  where  appearance 
is  of  minor  importance,  although  for  reasons  of  economy  or  other- 
wise they  are  sometimes  used  for  front  walls. 

They  are  often  made  without  much  regard  to  color,  smooth- 
ness of  surface,  or  sharpness  of  edges. 

Face,  front  or  pressed  brick  include  those  made  with  greater 
care  and  usually  from  better  grades  of  clay,  much  consideration 
being  given  to  their  uniformity  of  color,  even  surface  and  straight- 
ness  of  outline.  In  recent  years,  however,  there  has  been  a 
departure  from  some  of  these  surface  characters. 

Enameled  brick  include  those  which  have  a  coating  of  enamel, 
either  bright  or  dull,  on  one  and  sometimes  two  surfaces. 

Glazed  brick  differ  from  enameled  brick  in  being  coated  with  a 
transparent  glaze  instead  of  an  opaque  enamel.  They  are  more 
used  in  Europe  than  in  the  United  States. 

The  following  terms  are  used  more  or  less  in  the  trade. 

Air  Brick.  Hollow  or  pierced  brick  built  into  wall  to  allow 
passage  of  air. 

Arch  Brick.  This  term  may  be  applied  to  either  wedge-shaped 
brick  used  for  the  voussoir  of  an  arch,  or  to  brick  taken  from  the 
arches  of  a  kiln.  The  latter  type  are  hard  burned  and  sometimes 
even  rough  and  twisted  by  excessive  heating. 

Ashlar  Brick.  A  term  often  applied  to  certain  brick,  whose 
one  edge  is  rough  chiseled  to  resemble  rock-faced  stone. 

Clinker  Brick.    A  very  hard  burned  brick. 

259 


260  BUILDING   STONES   AND   CLAY-PRODUCTS 

Compass  Brick.     Same  as  first  meaning  for  arch  brick. 

Dutch  Brick.  Defined  by  Sturgis  as  a  hard,  light  colored, 
paving  brick,  used  in  England.  Originally  made  in  Holland. 

Fire  Brick.     One  that  stands  a  high  degree  of  heat. 

Flashed  Brick.  This  includes  those  pressed  brick  which  have 
had  their  edges  darkened  by  special  treatment  in  firing.  This 
color  is  superficial  and  may  range  from  a  light  gold  to  a  rich 
reddish  brown. 

Furring  Brick.  Hollow  brick  for  lining  or  furring  inside  of  wall. 
Usually  common  brick  size,  with  surface  grooved  to  take  plaster. 

Hollow  Brick.  Brick  molded  with  hollow  spaces  and  used  for 
partitions,  etc. 

Norman  Tile.  Brick  having  the  dimensions  12  by  2\  to  2-| 
by  4  inches. 

Ornamental  Brick.  Those  with  surface  ornamented  with  a 
relief  design.  They  are  not  necessarily  of  conventional  shape, 
but  may  be  of  square  outline.  Some  would  include  under  this 
heading  all  brick  which  are  not  of  plain  rectangular  character. 
This  would  then  include  angle  brick,  bullnose  brick,  beaded 
brick,  cover  brick,  and  all  shapes  which  have  an  ornamental 
surface  pattern. 

Pale  Brick.  Underburned  brick.  Usually  of  lighter  color 
than  normally  burned  ones  in  same  kiln.  They  are  often  porous 
and  soft,  and  used  mostly  for  backing. 

Paving  Brick.  One  of  low  absorption  and  good  hardness 
and  abrasive  resistance,  which  is  used  for  paving  purposes. 

Pompeiian  Brick.  These  are  of  the  same  size  as  Roman  tile 
(q.  v.),  but  are  a  medium  dark  shade  of  flashed  brick,  with  a 
brownish  body  covered  with  iron  spots.  The  two  terms  Roman 
and  Pompeiian  have  been  very  loosely  used. 

Pressed  Brick.  A  loosely  used  term,  applied  to  smooth-faced 
and  smooth-edged  brick,  made  either  by  the  dry  press  or  by 
the  softer  mud  processes  and  then  repressed. 

Rock-face  Brick.  Those  with  surface  chiseled  to  imitate  cut 
stone. 

Roman  Tile.  Brick,  usually  either  dry  pressed  or  stiff-mud 
repressed,  and  12  by  i|  by  4  inches  in  size. 


PLATE  XLV,  Fig.  i.  — Ornamental,  dry -pressed  brick. 


PLATE  XLV,  Fig.  2.  —Tapestry  brick.      (Photo  copyrighted  by  J.  Parker  Fiske.) 


261 


BUILDING  BRICKS  263 

Salmon  Brick.  Soft,  imperfectly  burned  brick.  So  called  on 
account  of  their  color.  Same  as  pale  brick. 

Sewer  Brick.  A  general  term  applied  to  those  common  brick 
which  are  burned  so  hard  as  to  be  practically  non-absorbent. 
They  are,  therefore,  adapted  for  use  as  sewer  linings. 

Slop  Brick.  A  name  sometimes  applied  to  those  made  by  the 
soft-mud  process. 

Stock  Brick.  A  term  sometimes  applied  to  the  better  selected 
bricks  from  a  kiln. 

Tapestry  Brick.  These  are  brick  made  by  the  stiff-mud  pro- 
cess, and  having  their  surfaces  roughened  by  cutting  a  thin  slice 
off  the  brick  by  a  wire.  They  are  much  used  nowadays  for 
fronts. 

RAW  MATERIALS  USED   FOR  BUILDING  BRICK. 

It  may  be  stated,  as  a  general  proposition,  that  the  higher 
grades  of  brick  are  usually  made  of  the  better  grades  of  clay. 

At  some  yards  or  in  some  districts,  the  same  clay  may  be  used 
for  both  common  and  pressed  brick,  in  which  case  the  latter 
are  manufactured  with  greater  care. 

Common  Brick.  The  clays  and  shales  used  for  common  brick 
are  usually  of  a  low  grade,  and  in  most  cases  red-burning.  Cal- 
careous clays  giving  a  cream-colored  product  are  much  employed 
in  some  districts,  as,  for  example,  in  Wisconsin,  Michigan  and 
Illinois,  but  this  is  largely  because  of  necessity  and  not  choice. 
The  main  requisites  are  that  they  shall  mold  easily  and  burn 
hard  at  as  low  a  temperature  as  possible,  with  a  minimum  loss 
from  cracking  and  warping. 

Unfortunately  but  little  care  is  often  used  in  the  selection  of 
clay  for  common  brick,  and  the  product  shows  it. 

Lime  pebbles,  if  present,  should  be  either  crushed  or  screened 
out,  otherwise  they  are  sure  to, cause  cracking  and  bursting  after 
burning. 

Pressed  Brick.  Pressed  brick  are  now  often  made  from  a 
higher  grade  of  clay.  The  kinds  employed  fall  mostly  into  one 
of  three  groups,  namely:  (i)  red-burning  clays;  (2)  white- 
burning  clays;  (3)  buff-burning  clays,  usually  of  at  least  semi- 
refractory  character. 


264  BUILDING  STONES  AND   CLAY-PRODUCTS 

The  physical  requirements  of  a  pressed-brick  clay  are:  (i) 
uniformity  of  color  in  burning,  (2)  freedom  from  warping  or 
splitting,  (3)  absence  of  soluble  salts,  and  (4)  sufficient  hardness 
and  low  absorption  after  burning.  The  first  requisite  is  perhaps 
not  as  rigidly  adhered  to  as  formerly. 

Red-burning  clays  were  formerly  much  used,  and  the  Phila- 
delphia red  brick  are  well  known  to  many  architects.  Cream- 
colored  brick,  made  of  calcareous  clays,  such  as  the  Milwaukee 
brick,  were  also  widely  employed  at  one  time.  But  in  recent 
years  buff-burning,  semi-refractory  and  refractory  clays  have 
found  wide-spread  favor  among  pressed-brick  manufacturers, 
partly  on  account  of  their  color  and  partly  because  coloring 
materials  can  be  effectively  added  to  them.  Manganese  in 
powdered  or  granular  form  is  the  coloring  agent  most  commonly 
employed. 

Enameled  Brick.  The  clays  used  for  these  are  similar  to  those 
employed  in  the  manufacture  of  buff  pressed  brick.  The  enamel 
is  an  artificial  mixture  which  must  conform  to  the  clay  body  to 
avoid  cracking  or  scaling  off  of  the  coat.  It  is  in  turn  covered 
by  a  glaze. 

METHODS   OF  BRICK  MANUFACTURE. 

These  may  be  briefly  taken  up  in  order  to  point  out  their 
influence  on  the  character  of  the  products  and  some  other  details 
of  importance  to  the  architect  or  engineer. 

The  methods  employed  in  the  manufacture  of  common  and 
pressed  brick  are  usually  similar,  the  differences  being  chiefly 
in  the  selection  of  material,  degree  of  preparation  and  amount 
of  care  taken  in  burning. 

The  manufacture  of  brick  may  be  separated  into  the  follow- 
ing steps:  preparation,  molding,  drying  and  burning. 

Preparation.  This  stage  might  be  divided  into  two  parts, 
viz.,  (i)  crushing  and  (2)  tempering  or  mixing.  Hard  shales 
and  very  tough  clays  usually  have  to  be  broken  up  by  proper 
machinery,  in  order  to  facilitate  the  admixture  of  water  to  them 
if  they  are  to  be  used  wet,  or  if  to  be  pressed  in  a  dry  condition 
they  can  be  pulverized  and  then  screened.  The  coarse  texture 
of  some  dry-press  brick  is  due  to  insufficient  grinding. 


BUILDING  BRICKS  265 

If  soft,  the  clay,  mixture  of  clays,  or  clay  and  sand  can  be 
charged  right  into  the  tempering  machine. 

In  some  cases  weathering  of  the  clay  precedes  the  mixing,  the 
crushing  being  left  out.  This  exposure  to  the  weather  may  often 
benefit  the  clay  and  cure  some  faults;  in  other  cases  it  is  of 
injury. 

The  tempering  or  mixing  is  an  important  stage  in  the  process 
and  the  more  thoroughly  done  the  greater  the  homogeneity  of 
the  product.  At  many  small  yards,  and  even  some  large  ones, 
as  in  the  Hudson  River  district,  the  rawmaterial  is  simply  dumped 
into  a  pit,  water  poured  on  and  the  mass  allowed  to  soak  over 
night,  or  at  others  the  clays  are  put  into  a  circular  pit  (ring  pit) 
in  which  a  wheel  revolves  following  a  spiral  path,  thus  cutting 
and  mixing  the  clay.  In  more  modern  works  the  raw  material, 
however,  is  mixed  in  a  pug  mill,  consisting  of  a  semi-cylindrical 
trough  in  which  there  revolves  a  horizontal  shaft  set  with  knife 
blades.  The  clay,  being  fed  into  this  with  water,  becomes  dis- 
integrated and  mixed. 

Wet  pans,  consisting  of  heavy  rolls  set  in  a  revolving  pan,  per- 
form a  similar  function. 

In  all  tempering  it  is  essential  to  mix  and  disintegrate  the  clay, 
for  if  this  is  not  done  lumps  may  be  left,  which  not  only  tend  to 
cause  cracking  in  drying  and  burning,  but  may  also  reduce  the 
transverse  strength.  Pebbles  left  in  the  clay  give  similar  trouble. 

Since  pug  mills  are  continuous  in  their  action,  a  greater 
quantity  of  clay  can  be  handled  per  machine  in  a  given  time  than 
in  the  case  of  some  of  the  other  machines  used. 

Molding.  Brick  are  molded  by  one  of  four  methods,  namely: 
soft  mud,  stiff  mud,  dry  press  and  semi-dry  press.  In  reality 
there  is  not  so  much  difference  between  the  last  two. 

Soft-mud  Process.  In  this  method  the  clay,  or  mixture  of 
clays,  is  mixed  with  water  to  the  consistency  of  a  soft  mud  or 
paste  and  pressed  into  wooden  molds.  Since,  however,  the  wet 
clay  is  sticky  and  likely  to  adhere  to  a  wooden  surface,  the  molds 
are  usually  sanded  each  time  before  being  filled,  in  order  to  facili- 
tate the  delivery1  of  the  brick.  Soft-mud  brick  are  molded 
1  At  some  hand-power  yards,  water  is  used  instead  of  sand. 


266 


BUILDING  STONES  AND   CLAY-PRODUCTS 


either  by  hand  or  in  a  machine,  the  latter  being  operated  by 
horse  or  steam  power.  The  soft.mud  machine  (Fig.  7), 

consists  essentially  of  an  upright 
box  of  wood  or  iron,  in  which  there 
revolves  a  vertical  shaft  bearing  sev- 
eral blades,  while  attached  to  the 
bottom  of  the  shaft  is  a  curved  arm 
that  forces  the  clay  into  the  press 
box.  The  molds  after  being  sanded 
are  shoved  underneath  the  machine 
from  the  side  and  move  forward  to 
a  position  underneath  the  press  box. 
As  the  mold  reaches  this  position  the 
plunger  descends  and  forces  the  soft 
clay  into  the  compartments  of  the 
mold.  This  filled  mold  box  is  then 
pushed  forward  automatically  upon 
the  delivery  table  while  an  empty 
one  moves  forward  to  take  its  place. 
As  soon  as  the  mold  is  delivered,  its 
upper  surface  is  "struck"  off  by 
means  of  an  iron  scraper.  The  mold 
is  then  emptied  onto  pallets  on  which 
the  brick  are  carried  to  the  drying 
racks,  or  the  mold  is  taken  to  the 
drying  floor  where  the  brick  are 
dumped  out. 


Fig.  7.  —  Soft-mud  brick  machine. 


A  soft-mud  machine  operated  by  steam  power  will  commonly 
turn  out  about  25,000  brick  per  day.  If  molded  by  hand  from 
2500  to  3000  are  usually  made. 

Soft-mud  brick  can  be  easily  recognized  by  their  external 
appearance  (Plate  XL VI,  Fig.  i),  for  on  account  of  the  method 
of  molding  employed,  they  show  five  sanded  surfaces,  while  the 
sixth  surface  will  be  somewhat  rough  due  to  excess  of  clay  being 
wiped  off  even  with  the  top  of  the  mold. 

The  process  is  adapted  to  a  wider  range  of  clays  than  any  of 
the  others  and  possesses  the  advantage  of  producing  not  only  a 
brick  of  very  homogeneous  structure  but  one  that,  if  properly 
burned,  is  rarely  affected  by  frost  action. 

Those  which  are  hand  molded  are  often  more  porous  than  the 
machine-molded  ones,  but  this  may  be  partly  due  to  the  char- 
acter of  the  raw  materials  employed  and  handling  of  the  burn- 


PLATE  XL  VI,  Fig.  i.  —  Common  red  soft -mud  brick.  The  roughness  of  upper 
surface  is  due  to  striking  off  excess  of  clay  in  mold.  The  other  two  exposed 
surfaces  are  sanded  ones. 


PLATE  XL VI,  Fig.  2.  —  A  common  soft-mud  brick.  The  iron  oxide  was  not  evenly 
distributed  in  the  day,  but  was  present  in  lumps  and  hence  caused  the 
blotches. 


267 


BUILDING  BRICKS  269 

ing.  Soft-mud  brick,  unless  repressed,  lack  very  sharp  corners 
and  straight  edges.  Their  fracture  may  also  show  more  pebbly 
particles  than  that  of  brick  formed  by  the  other  two  processes. 

On  a  later  page  will  be  found  the  tests  of  a  number  of  soft- 
mud  brick. 

Stiff-mud  process.  In  this  method  the  clay  is  mixed  with 
sufficient  water  to  make  a  stiff  plastic  mass,  and  the  principle 
of  the  process  consists  in  taking  the  clay  thus  prepared  and  forc- 
ing it  through  a  die  in  the  form  of  a  rectangular  bar,  which  is 
then  cut  up  into  bricks. 

The  form  of  machine  (Fig.  8)  most  commonly  employed  is  known  as  the  auger 
machine,  and  consists  of  a  cylinder  closed  at  one  end,  except  for  a  feed  hopper  on 
top,  but  at  the  other  end  tapering  off  to  a  rectangular  die  whose  cross  section  is  the 
same  as  either  the  end  or  the  largest  side  of  a  brick.  Within  this  cylinder,  which 
is  set  in  a  horizontal  position,  there  is  a  shaft,  carrying  blades  similar  to  those  of 
a  pug  mill,  but  at  the  end  of  the  shaft  nearest  the  die  there  is  a  tapering  screw. 
The  die  is  properly  lubricated  to  prevent  sticking  of  the  clay. 

The  tempered  clay  is  charged  into  the  cylinder  at  the  end  farthest  from  the  die, 
is  mixed  by  the  blades  on  the  revolving  shaft,  and  at  the  same  time  moved  forward 
until  seized  by  the  screw  and  forced  through  the  die.  This  forcing  of  the  clay 
through  the  opening,  which  is  small  as  compared  with  the  full  cross  section  of  the 
cylinder,  results  in  a  marked  compression  of  the  clay,  and  there  is  also  some  friction 
between  the  sides  of  the  bar  and  the  interior  of  the  die,  causing  the  center  of  the 
stream  of  clay  to  move  faster  than  the  outer  portion.  If  the  friction  between  clay 
and  die  is  greater  than  coherence  between  clay  particles,  a  tearing  of  the  clay, 
especially  on  the  edges  of  the  bar,  results,  producing  serrations  like  the  teeth  of  a 
saw.  This  may  not  seriously  weaken  the  brick,  however.  The  twisting  action  of 
the  screw  at  the  end  of  the  shaft  also  produces  a  spirally  laminated  structure 
(Plate  XL VII)  in  some  clays,  which  is  often  most  pronounced  in  very  plastic  clays. 

As  the  bar  of  clay  issues  from  the  machine  it  is  received  on  the  cutting  table, 
where  it  is  cut  up  into  bricks  by  wires,  fastened  either  in  parallel  arrangement  on  a 
frame,  or  fastened  to  the  forked  ends  of  spokes  of  a  wheel.  As  the  wires  make  a 
somewhat  rasping  cut,  the  cut  surfaces  are  always  recognizable  on  a  stiff-mud  brick. 

Brick  made  in  auger  machines  are  either  end  cut  or  side  cut, 
depending  on  whether  the  area  of  the  cross  section  of  the  bar  of 
clay  corresponds  to  the  end  or  side  of  a  brick,  and  consequently 
the  mouth  of  the  die  varies  in  size  and  shape. 

The  stiff-mud  process,  while  one  of  high  capacity,  —  60,000  or 
even  100,000  brick  per  day  being  produced  without  difficulty,  — 
is  not  adapted  to  all  kinds  of  clays,  those  of  medium  plasticity 
giving  perhaps  the  best  results,  so  that  defective  brick  are 
sometimes  the  fault  of  the  process  and  not  of  the  clay. 


Plate  XL  VII.  —  Section  of  stiff -mud  brick  showing  laminations. 


271 


PLATE  XL VIII.  —  Dry-press  brick  machine.     (After  Ries,  N.  Y.  State  Museum, 

Bull.  35,  1900.) 


273 


BUILDING  BRICKS  275 

A  stiff-mud  brick  can  be  easily  recognized  by  the  four  smooth 
surfaces  and  the  two  cut  faces,  which  show  the  tearing  action 
of  the  cutting  wires.  The  laminations  are  to  be  looked  for  on 
these  last-mentioned  surfaces.  In  some  brick  they  are  so  pro- 
nounced as  to  cause  the  different  shells  to  separate  somewhat 
in  burning. 

Dry -press  and  Semi-dry-press  Process.  This  process  is  com- 
monly used  for  the  production  of  front  brick,  but  in  some  states 
is  extensively  employed  even  for  common  brick  manufacture. 
The  clay  is  first  allowed  to  dry  out  under  sheds  until  it  has  not 
more  than  12  or  15  per  cent  moisture,  and  then  disintegrated  in 
suitable  machines,  after  which  it  is  screened  and  the  screenings 
conducted  into  the  hopper  of  the  press.  The  process  consists 
essentially  in  pressing  this  partly  dry,  pulverized  clay  in  steel 
molds. 

The  molding  machine  (Plate  XL VIII)  consists  of  a  steel  frame  of  varying  height 
and  heaviness,  with  a  delivery  table  about  three  feet  above  the  ground,  and  a  press 
box  sunk  into  the  rear  of  it.  The  charger  is  connected  with  the  clay  hopper  by 
means  of  a  canvas  tube  and  forms  a  framework  which  slides  back  and  forth  over 
the  molds.  It  is  filled  on  the  backward  stroke,  and  on  its  forward  stroke  lets  the 
clay  fall  into  the  mold  box.  As  the  charger  recedes  to  be  refilled,  a  plunger  de- 
scends, pressing  the  clay  into  the  mold;  but  at  the  same  time  the  bottom  of  the 
mold,  which  is  movable,  rises  slightly,  and  the  clay  is  subjected  to  greater  pressure, 
which  may  be  repeated  after  a  moment's  interval.  The  plunger  then  rises,  while 
the  bottom  of  the  mold  also  ascends,  pushing  the  freshly  molded  brick  to  the  level 
of  the  delivery  table.  They  are  then  shoved  forward  as  the  charger  advances  to 
refill  the  molds. 

In  order  to  release  at  least  some  of  the  compressed  air  imprisoned  in  the 
clay,  the  dies  are  provided  with  air  vents. 

The  advantages  claimed  for  the  dry-press  process  are  that  in 
one  operation  it  produces  a  brick  with  sharp  edges  and  smooth 
faces.  Air  drying  is  eliminated,  but  there  is  considerable  mois- 
ture to  be  driven  off  in  the  kiln  during  the  early  stages  of  burning. 
Dry-press  brick,  unless  well  vitrified,  often  show  a  granular 
structure  because  the  clay  grains  do  not  amalgamate  as  they 
could  if  the  clay  were  mixed  wet,  and  if,  because  of  hardness, 
the  clay  does  not  break  down  easily,  these  granulations  may 
be  very  noticeable.  Dry-pressed  brick,  if  hard-burned  may  be 
just  as  strong  as  others,  but,  if  not  hard  burned,  they  fre- 
quently show  a  much  higher  absorption  than  if  the  clay  had 


276 


BUILDING   STONES  AND   CLAY-PRODUCTS 


been  molded  wet.     The  capacity  of   a  dry-press  machine  is 
about  the  same  as  that  of  a  soft-mud  one. 

Repressing.  Many  soft-mud  and  stiff-mud  brick  that  are  to 
be  used  for  fronts  are  improved  in  appearance  by  repressing. 
The  process  consists  in  putting  them  in  a  machine  shortly  after 
molding,  in  which  they  receive  a  second  pressing.  The  main 
object  of  this  is  to  straighten  the  edges  and  smoothen  the  surface, 
and  in  many  cases  some  design  is  imprinted  in  the  surface  of  the 
brick.  The  brick  are  usually  slightly  smaller  after  this  treat- 
ment. The  pressure  which  the  brick  get,  together  with  the  use 
of  some  lubricant  and  the  slipping  in  and  out  of  the  mold, 
polishes  the  surface  so  at  times  as  to  form  a  tough  exterior  skin 
which  strengthens  their  resistance  to  disintegrating  influences. 
Repressing  may  also  make  the  brick  denser  and  even  stronger,  as 
shown  by  the  following  tests  which  were  made  on  some  hand- 
molded,  soft-mud,  New  Jersey  samples. 


Crushing  strength. 

I. 

II. 

Before  repressing. 

After  repressing. 

Crushing  strength,  pounds  per  square  inch.  .  . 
Transverse  strength  modulus  of  rupture  
Absorption  

3107 
440 
12.09% 

n 

4  •  304 
613 
9-75% 

Drying.  Bricks  made  by  either  the  stiff-mud  or  soft-mud 
process  have  to  be  freed  from  most  of  their  water  before  they  can 
be  burned. 

For  the  purpose  of  this  discussion  it  is  not  necessary  to  go  into 
a  detailed  description  of  the  methods  of  drying,  but  certain 
features  of  interest  or  value  to  the  architect  may  be  pointed  out. 

At  many  common  brickyards  the  product  is  dried  on  floors 
exposed  to  the  sun  or  air.  This  process  in  no  way  detracts  from 
the  quality  of  the  product,  but  can  be  carried  on  only  during 
those  months  when  the  temperature  is  above  freezing.  More- 
over, a  yard  employing  this  method  is  of  limited  capacity  unless 
a  large  floor  space  is  available.  During  rainstorms  the  surface 
of  the  brick  becomes  roughened  by  the  beating  of  the  raindrops, 
and  such  washed  brick  are  not  as  a  rule  salable,  although  if 


PLATE  XLIX,  Fig.  i. — Common  red  soft-mud  brick  which  has  been  split  by  air 
slaking  of  calcined  lime  pebbles;   the  two  white  spots  are  the  pebbles. 


PLATE  XLIX,  Fig.  2.  — Repressed  brick.    The  rounded  edges  and  corners  as  well 
as  the  grooves  were  produced  in  the  repressing. 


277 


BUILDING  BRICKS  279 

burned  they  do  not  lack  in  strength.  The  practice  of  drying  the 
brick  on  racks  under  sheds  is  an  improvement.  At  many  com- 
mon brickyards,  and  all  those  where  front  brick  are  manufac- 
tured, artificial  heat  is  used  for  drying,  the  brick  being  stacked 
on  cars  and  run  into  tunnels,  which  are  heated  by  appropriate 
means.  This  system  permits  the  operation  of  the  plant  through- 
out the  year  and  possesses  an  advantage  over  the  open-air 
system.  The  drying,  however,  is  not  necessarily  more  rapid. 
Indeed,  some  clays  have  to  be  tunnel  dried  with  great  care  to 
prevent  cracking  of  the  product. 

Burning.  In  this  stage  of  the  manufacture,  the  bricks  are 
converted  into  their  permanent  durable  form,  the  process  being 
carried  out  in  kilns  of  one  type  or  another. 

The  temperature  required  for  burning  brick  will  vary  with  the 
clay  and  density,  degree  of  hardness  and  color  desired,  the  same 
clay  yielding  different  results  when  fired  at  different  tempera- 
tures. Common  brick  are  usually  fired  at  a  red  heat,  and  not 
always  even  a  bright  red,  while  pressed  brick,  especially  if  made 
of  fire  clay,  are  burned  at  a  much  higher  temperature.1  Still,  even 
in  the  same  kiln,  we  oftentimes  find  a  difference  in  temperature 
in  different  parts,  and  this  alone  may  produce  variations  in  the 
character  of  the  product  in  any  lot. 

The  kilns  used  might  be  divided  into  two  groups,  viz.,  tem- 
porary and  permanent,  and  the  latter  still  further  into  inter- 
mittent and  continuous. 

The  use  of  temporary  kilns  is  confined  to  common  brick,  but 
not  necessarily  to  small  yards.  Such  kilns  are  called  scove 
kilns  (Plate  L,  Fig.  i).  For  these,  the  brick  are  piled  up  in  large 
rectangular  masses  from  thirty  to  fifty-four  courses  high,  depend- 
ing on  the  clay.  Alternate  layers  head  in  the  same  direction, 
and  at  right  angles  to  those  next  above  and  below. 

In  building  up  the  kiln,  a  series  of  parallel  arches  is  left  running 
through  the  mass  from  side  to  side.  After  the  bricks  are  set  up 

1  Some  brickmakers  judge  the  completion  of  burning  by  test  pyramids  called 
Seger  cones.  These  are  artificial  mixtures  of  definite  fusion  points.  Most  common 
brick  are  burned  at  about  cone  oio  whose  theoretic  melting  point  is  1050°  C.,  while 
pressed  brick  are  often  fired  to  cone  7  or  8,  about  1280°  C. 


280  BUILDING  STONES  AND   CLAY-PRODUCTS 

they  are  surrounded  by  a  wall  of  bricks  two  layers  deep,  and  the 
whole  outside  daubed  with  wet  clay  to  prevent  the  entrance  of 
cold  air  during  burning.  The  top  of  the  kiln  is  then  closed  by  a 
layer  of  brick  laid  close  together  to  keep  the  heat  in. 

In  some  cases,  permanent  side  walls  with  fire  boxes  are  built. 

It  is  very  easily  seen  that  the  scove  kiln  will  give  a  vari- 
able product.  Those  bricks  around  the  arches  receive  the 
most  heat,  those  in  the  farthest  corners  the  least,  while  the 
normally  burned  ones  are  mainly  in  the  center.  Sorting  is 
therefore  necessary  in  every  case.  Many  brick  burned  in  this 
manner  have  coal  dust  added  to  the  clay  during  molding,  so  that 
the  burning  of  this  during  firing  will  add  to  the  temperature  of 
the  kiln.  The  ash  from  these  coal  specks  is  often  seen  in  the 
interior  of  the  brick  and  supposed  by  many  to  greatly  detract 
from  their  strength.  This,  however,  is  not  probable. 

The  permanent  intermittent  kilns,  which  are  used  for  burning 
all  kinds  of  brick,  have  permanent  walls  and  roof,  and  yield  much 
better  results.  They  are  either  of  up-  or  down-draft  character. 
In  the  former  the  heat  from  the  fire  box  enters  the  kiln  chamber 
in  the  lower  part,  passes  up  through  the  brick  and  out  through 
flues  at  the  top.  In  the  latter  the  heat  enters  the  upper  part  of 
the  kiln  chamber  first,  passes  down  through  the  kiln  and  is 
drawn  out  through  flues  at  the  bottom.  The  brick,  therefore, 
which  receive  the  most  heat  will  be  those  in  that  portion  of  the 
chamber  which  the  fire  enters.  For  this  reason  the  bricks  in  the 
bottom  of  up-draft  kilns  are  often  harder  burned  than  those  at 
the  top,  while  in  down-draft  kilns  the  reverse  is  true.  The  larger 
the  kiln  the  more  difficult  it  is  to  get  uniform  results  throughout. 
This  is  especially  noticeable  at  times,  where  the  brick  are  being 
burned  for  color.  The  same  kiln,  if  a  large  one,  might  yield 
eight  or  ten  different  shades. 

In  the  continuous  system  of  burning,  the  kiln  is  composed  of 
a  series  of  compartments  or  chambers  separated  by  permanent 
or  temporary  walls,  these  being  connected  with  each  other  and 
also  with  the  stack  by  a  system  of  flues.  The  waste  heat  from 
any  given  chamber  is  utilized  by  being  drawn  through  several 
others  before  passing  to  the  stack  and  serves  to  heat  them  up  to 


PLATE  L,  Fig.  i.  — Setting  brick  for  a  scove  kiln. 
(After  Ries,  N.  J.  Geol.  Surv.,  VI,  1900.) 


PLATE  L,  Fig.  2.  —  Down-draft  kilns  used  for  burning  sewer  pipe. 
(Photo  from  Robinson  Clay- Product  Co.) 


281 


BUILDING  BRICKS  283 

a  certain  point,  beyond  which  the  firing  is  continued  by  the 
introduction  of  coal  slack  through  openings  in  the  chimney. 
The  use  of  these  kilns  is  increasing,  but  they  do  not  give  good 
results  where  color  effects  are  desired. 

Whatever  system  of  burning  is  employed,  care  and  slowness 
are  essential.  The  clay  must  first  be  carefully  heated  to  drive 
off  the  moisture.  If  carbon  or  sulphur  are  present  these  must 
also  be  carefully  expelled  when  the  kiln  reaches  a  red  heat,  and 
before  fire  shrinkage  begins,  in  order  to  prevent  the  formation 
of  black  cores  and  swollen  brick. 

No  brickmaker  ever  gets  100  per  cent,  or  probably  even  85 
per  cent  perfect  brick.  Not  a  few  are  roughened,  discolored 
and  distorted  by  overfiring  or  other  causes,  and  these,  in  the 
manufacturer's  opinion,  have  usually  been  regarded  as  worthless. 
But  it  is  these  rejects  that  in  many  cases  have  appealed  to  the 
architect,  and  as  a  result  of  the  demand  for  them,  the  "  culls  " 
have  not  only  assumed  a  good  market  value,  but  in  some  dis- 
tricts the  brickmaker  has  been  called  upon  to  turn  out  hundreds 
of  them.  This  may  give  him  even  more  trouble  than  producing 
a  kiln  of  normally  burned  brick,  and  he  consequently  demands 
a  good  price  for  them. 

At  one  brick  works,  for  example,  the  manufacturer  was  called 
upon  to  fill  a  large  order  for  some  bluish-black  brick  with  a 
blistered  and  pimpled  surface.  This  was  accomplished  only  by 
careful  overfiring  and  shutting  off  as  much  air  as  possible  from 
the  kiln  during  the  later  stages  of  burning. 

In  a  large  city  of  the  Pacific  Coast,  dozens  of  exterior  chimneys 
on  private  dwellings  are  constructed  of  the  warped,  partly 
fused,  overburned  product  from  a  local  paving-brick  works.  If 
these  had  not  caught  the  fancy  of  the  architect  they  would  be  a 
loss  to  the  manufacturer. 

The  smooth-faced,  monotone,  evenly  burned  brick  is  not  in 
favor  at  the  present  time,  except  for  special  purposes. 

Comparison  of  Brick  made  by  Different  Processes.  The 
question  is  often  asked,  how  brick  made  by  different  processes 
compare  with  each  other.  A  few  points  on  this  may,  therefore, 
be  desirable. 


284  BUILDING  STONES  AND   CLAY-PRODUCTS 

Soft-mud  brick  possess  a  more  homogeneous  structure  than 
those  made  by  other  processes,  as  well  as  being  thoroughly  dur- 
able when  well  burned.  They  lack  the  smooth  surface  and  sharp 
corners  of  the  dry-pressed  ones.  Stiff-mud  brick  when  made  of 
the  proper  clay  and  molded  in  a  machine  adapted  to  the  raw 
material  also  show  a  good  structure,  but  the  laminations  found 
in  many  are  an  objection.  It  is  easier  to  make  a  mis-selection  of 
clay  in  this  process  than  in  the  soft  mud. 

Dry-press  bricks  present  a  finished  appearance  without  further 
treatment,  not  requiring  repressing  as  in  the  case  of  soft-mud 
and  stiff-mud  wares.  Owing  to  the  granular  character  of  the 
clay  there  is  a  lack  of  cohesion  between  the  particles,  and  the 
resulting  brick  is  softer  than  one  made  by  the  mud  processes, 
unless  it  is  well  burned. 

Taking  the  results  of  a  large  number  of  tests  no  one  method 
gives  a  brick  of  higher  average  strength  or  density  than  the 
others. 

Testing  of  Brick.  The  tests  which  can  be  applied  to  bricks  are: 
i,  crushing  test;  2,  transverse  test;  3,  absorption  test  and  porosity; 
4,  abrasion  test;  5,  frost  resistance;  6,  fire  test;  7,  permeability. 

All  of  these  are  rarely  carried  out.  Usually  it  is  only  i  and  3 
for  structural  brick,  and  i,  3  and  4  for  paving  brick. 

Crushing  Test.  The  test  to  determine  a  brick's  crushing 
strength  is  made  in  a  specially  constructed  machine.  Half 
bricks  are  usually  tested,  because  a  whole  brick  has  so  large  a 
surface  area  that  it  might  resist  greater  pressure  than  could  be 
applied  by  the  testing  apparatus. 

Before  crushing,  the  two  opposite  surfaces  of  the  brick  (in 
this  case  the  top  and  bottom)  must  either  be  ground  very  smooth 
and  parallel,  or  else  they  must  be  built  up  to  this  condition  by 
the  application  of  a  layer  of  plaster  of  Paris.  Paper  or  card- 
board are  sometimes  used  as  substitutes  for  plaster.  The  reason 
for  this  is  that  in  the  testing  machine  the  brick  is  set  between  two 
steel  surfaces  and  unless  its  surface  fits  perfectly  against  these 
the  pressure  will  not  be  evenly  distributed. 

In  order  to  show  the  effect  of  the  method  employed  in  pre- 
paring samples  for  the  crushing  tests,  some  experiments  were 


Lbs. 
6000 


5500 


5000 


4500 


4000 


3500 


8000 


2500 


2000 


1500 


1000 


€00 


Fig.  9.  —  Diagram  of  crushing  and  transverse  tests  made  on  soft-mud  bricl 

and  the  lower  end  the  modulus  of  ruptur 


)m  Wisconsin.    The  upper  end  of  each  line  represents  the  crushing  strength 
(After  Ries,  Wis.  Geol.  Surv.,  Bull.  XV.)  285-288 


BUILDING  BRICKS 


289 


made  by  the  Iowa  Geological  Survey 1  on  a  parallel  series,  con- 
sisting (i)  of  accurately  ground  2-inch  cubes,  and  (2)  of  one- 
third  of  a  brick  placed  flatwise,  with  plaster  of  Paris  between  the 
brick  surface  and  the  plate  of  the  testing  machine. 

The  results  obtained  with  the  plaster  of  Paris  were  invariably 
lower,  sometimes  as  much  as  6000  pounds  per  square  inch,  but 
mostly  not  over  1000  pounds.  In  a  few  cases  the  plaster  series 
gave  higher  tests. 

Brick  show  a  wide  range  of  crushing  strength,  running  from 
as  low  as  500  pounds  per  square  inch  up  to  12,000  or  15,000 
pounds,  or  even  more. 

We  cannot,  in  the  present  state  of  our  knowledge,  lay  down 
any  rule  bearing  on  relation  of  method  of  manufacture  to  crush- 
ing strength. 

It  may  be  said  in  general,  however,  that  the  crushing  strength 
increases  usually  with  the  hardness  of  burning.  The  following 
figures  bring  out  this  point: 


Crushing  strength, 
normal  burned. 

Pounds  per  square 
inch,  hard  burned. 

I 
II 
III 

4933 
993-3 
1500 

11,058 
1,996.6. 
4,852.5 

Common  brick  often  show  a  crushing  strength  of  2500  to 
3000  pounds  per  square  inch  and  even  more. 

Hard-burned  brick  not  infrequently  run  10,000  and  12,000 
pounds  and  sometimes  very  much  higher. 

There  is  not  necessarily  any  direct  relation  between  the  crush- 
ing strength  and  the  transverse  strength,  abrasive  resistance, 
absorption  or  frost  resistance. 

Repressing  often  increases  the  crushing  strength. 

The  crushing  strength  increases  primarily  with  the  increased 
hardness  of  burning,  and  secondarily  with  the  decrease  in  pore 
space. 

A  burned  clay  product  will  not  be  uniformly  strong  in  all 
directions,  and  the  method  of  manufacture  may  impart  to  it 
1  Iowa  Geol.  Surv.,  Vol.  XIV,  p.  562. 


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Fig.  10.  —  Diagram  showing  absorption  tests  on  Wisconsin  soft-mud  brick  after 
290  forty-eight  hours  immersion. 


Lbs. 
8000 


7500 


7000 


6500 


6000 


5000 


4500 


3000 


1500 


1000 


Fig.  ii.  — Diagram  of  crushing  and  transverse  tests  on  Wisconsin  stiff-mud  brick, 
(After  Ries,  Wis.  Geol.  Surv.,  Bull.  XV.)  291 


2Q2 


BUILDING   STONES   AND   CLAY-PRODUCTS 


greater  strength  along  one  plane  than  another.     Auger  lamina- 
tions may  be  regarded  as  influencing  abnormal  structure. 

As  a  matter  of  fact,  clay  products  are  never  taxed  beyond  their 
compressive  strength. 


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Fig.  12.  — Diagram  showing  absorption  tests  on  Wisconsin  stiff-mud  brick  after 
forty-eight  hours  immersion. 

In  testing  the  crushing  strength  of  a  brick,  the  latter  is  usually 
laid  flatwise.  Some  objection  has  been  raised  to  this  on  the 
ground  that  there  is  a  large  experimental  error  due  to  shape. 


BUILDING  BRICKS 


293 


Theoretically,  the  best  form  of  test  piece  is  that  of  a  cube,  or 
still  better  a  prism  of  square  cross  section,  the  height  of  which 
Ijhs.  is  i^  times  the  breadth,  as  this  gives  sym- 

metrical fracture  planes. 

A  custom  followed  in  Germany  is  to  use 
two  half  bricks  cemented  together  by  a  thin 
joint  of  Portland  cement  mortar.  This  gives 
a  prism  and  yields  satisfactory  results. 

An  advantage  claimed  for  testing  a  brick 
on  edge  is  that  the  failing  point  can  be  more 
sharply  detected  than  when  the  brick  is 
tested  flatwise. 

One  objection  to  testing  brick  on  edge  is 
that  it  does  not  represent  the  position  of  the 

brick  when  in  use ; 
however,  this  is  un- 
important, since 
the  compression 
strength  per  se 
has  no  practical 
value,  except  in  so 
far  as  it  differenti- 
ates between  good 
and  poor  materi- 
als. But  since  the 
flatwise  test  is 
liable  to  serious 
errors,  it  is  clear 
that  the  advan- 
tage must  lie  with 
the  edgewise 
method  which  af- 
fords more  reliable 
1Fig  13b  comparative  data. 

Fig.  13.  —  (a)  Diagram  of  crushing  and  transverse  tests  on  Wisconsin  dry-pressed 
brick.  The  upper  end  of  each  line  represents  the  crushing  strength  and  the 
lower  end  the  modulus  of  rupture.  (6)  Absorption  tests  of  same  series. 
(After  Ries,  Wis.  Geol.  Surv.,  Bull.  XV.) 


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294 


BUILDING  STONES  AND   CLAY-PRODUCTS 


It  is  not  possible  to  calculate  from  the  strength  on  edge  what 
it  will  be  when  the  brick  is  tested  flatwise,  or  vice  versa,  except 
for  one  and  the  same  brick,  since  the  structure  plays  such  an 
important  role. 

It  is  said  that  a  side-cut  brick  will  show  a  different  com- 
pressive  strength,  when  tested  on  edge,  from  an  end-cut  one  made 
from  the  same  clay. 

The  following  table  taken  from  the  War  Department's  report 
on  Tests  of  Metals,  etc.,  for  1895,  shows  that  the  compressive 
strength  of  a  wet  brick  is  usually  lower  than  that  of  a  dry  one. 

COMPRESSIVE    STRENGTH    OF    WET    AND    DRY    HALVES    OP 
THE   SAME   BRICK. 


Manufacturers. 

Description. 

Compressive  strength  per 
square  inch. 

Dry. 

Wet. 

Loss. 

Gay  Head  Clay  &  Brick  Co.,  Chelsea, 
Mass  

New  England  Steam  Brick  Co.,  Prov 
idence,  R.  I.  ... 

Buff  

Buff... 

Pounds. 
5,774 
5,570 
6,481 
2,639 
5,777 
7,888 
10,624 
11,353 
5,6oi 
9,655 
3,599 
10,712 
4,929 
16,019 
4,447 
15,842 
2,414 

11,942 
18,072 

12,000 

16,018 

7,724 

2,973 

Pounds. 
4,900 
5,346 
5,063 
2,321 
4,5o6 
8,917 
10,482 
8,088 
4,530 
6,230 
3,289 
9,902 
4,142 
14,822 
4,052 
11,273 
1,885 

7,941 
11,911 
12,652 

15,611 
7,037 

2,778 

Pounds. 
874 
244 
1418 
318 
1271 
—  1029 
142 
3265 
1071 
3425 
3io 
810 
787 
1197 
395 
4569 
529 

4001 
6161 
-652 

407 
687 

195 

Buff  speckled  
Firebrick  
Red    No.  I.. 

Red,  No.  2.... 
Red,  No.  3.. 

Red    No.  4.. 

Light  hard,  water  struck  . 
Hard  body  
Light  buff,  No.  55  
„  Paving  
:  Cream  white,  No.  I  
Light  red.  No.  3  
Cream  white,  No.  4  
(  Vitrified  paving,  A  
\  Fire,  No.  i  

Vitrified  paving  block  .  .  . 
f  Red,  No.  i  
(  Red,  No.  2.. 

The   Powhatan    Clay   Manufacturing 
Co.,  Richmond,  Va  

The  Coaldale  Brick  &  Tile  Co.,  Coal- 
dale,  Ala  
The  A.  O.  Jones  Brick  &  Terra  Cotta 
Co    Zanesville    O. 

Kansas  City  Hydraulic  Press   Brick 
Co.   Kansas  City,  Mo.  .  . 

Monticello  Brick  Works,  Monticello, 
Minn  
A.  Humphrey,  Minneapolis,  Minn  
Pacific  Clay  Manufacturing  Co.,  Los 
Angeles,  Cal  

Mean  
Relative  strength,  per  cent  .  .  . 

Face,  No.  2  
Light  chocolate,  No.  71  .  . 

8,039 

100 

6,835 
85 

1204 
15 

Transverse  Test.  This  is  a  more  important  test  even  than  the 
crushing  strength,  for,  while  the  brick  is  rarely  loaded  up  to  its 
crushing  limit,  it  is  sometimes  exposed  to  its  limit  of  elasticity 
and  cracked.  This  can,  perhaps,  be  better  understood  if  the 
manner  of  making  the  test  is  first  explained. 


BUILDING  BRICKS  295 

In  the  cross-breaking  test  a  whole  brick  is  placed  on  two 
rounded  knife-edge  bearings.  Pressure  is  applied  from  above,  at 
a  point  midway  between  the  two  supports,  until  the  brick  breaks 
in  two,  and  the  number  of  pounds  at  which  this  occurs  is  noted. 

It  is  evident  that  in  two  bricks  of  exactly  the  same  degree  of 
strength,  the  amount  of  pressure  necessary  to  break  them  will 
depend  upon  (i)  the  distance  between  the  supports  and  (2)  the 
cross  section  of  the  brick. 

The  farther  apart  the  supports  the  less  pressure  necessary  to 
break  the  brick,  and  the  greater  the  cross  section  the  greater 
the  pressure  necessary. 

Since  this  is  so,  it  is  necessary  that  for  purposes  of  com- 
parison all  results  of  the  breaking  strength  be  reduced  to  some 
uniform  expression  which  shall  take  account  of  the  differences 
in  length,  width  and  thickness  of  the  brick. 

The  most  accurate  expression  is  that  termed  the  modulus  of 
rupture,  which  is  calculated  from  the  following  formula : 

1  wl 

R  =  °7  7. ,  in  which 

2  oh2 

R  =  modulus  of  rupture, 

w  =  pressure  necessary  to  break  the  brick, 

/  =  distance  between  supports; 

b  =  breadth  of  brick, 

h  =  thickness  of  the  brick. 

Cavities,  pebbles  and  clay  lumps  seem  to  affect  the  transverse 
strength  more  than  the  crushing  strength. 

There  is  often  great  lack  of  uniformity  of  different  individual 
specimens  tested.  This  may  be  due  to  irregularity  in  burning, 
a  fact  often  overlooked  by  engineers  and  architects. 

The  transverse  test  indicates  the  character  of  the  brick's 
structure.  It  is  claimed  that  the  finer  grained,  more  uniform 
and  dense  the  structure  of  the  brick,  the  higher  its  transverse 
strength;  the  better  burned,  the  higher  the  transverse  strength. 

As  mentioned  above,  there  is  no  definite  relationship  between 
modulus  of  rupture  and  crushing  strength,  and  this  fact  is  also 
brought  out  in  the  tables. 


296  BUILDING  STONES  AND   CLAY-PRODUCTS 

Absorption  Test.  An  absorption  test  is  made  for  the  purpose 
of  determining  how  much  water  a  brick  will  absorb  when  soaked 
in  water,  it  being  supposed  by  many  engineers,  architects  and 
others  that  the  percer  tage  of  absorption  stands  in  direct  relation 
to  the  frost  resistance  of  the  brick.  This  is  not  so. 

In  the  first  place  there  are  several  ways  of  making  the  test, 
which  yield  somewhat  different  results.  It  may  be  made,  (i)  by 
complete  immersion,  usually  for  forty-eight  hours,  but  sometimes 
even  longer.  (2)  By  partial  immersion,  and  this  for  but  a  few 
hours,  or  longer,  there  being  no  standard  rule.  (3)  By  complete 
immersion  in  a  vacuum. 

In  discussing  these  it  should  be  remembered  that  in  making 
such  a  test  we  are  endeavoring  to  imitate  at  least  approximately 
the  conditions  to  which  the  brick  will  be  actually  exposed  when 
in  use,  and  that  we  are  not  doing  so  will  be  apparent  to  anyone 
on  a  moment's  reflection.  When  placed  in  a  wall,  a  brick,  unless 
set  in  damp  ground  or  water,  absorbs  moisture  only  from  one 
side,  the  side  exposed  to  the  weather  and  on  which  the  rain 
spatters.  So  it  probably  soaks  up  much  less  than  it  does  when 
tested  in  the  laboratory. 

In  whatever  way  the  absorption  test  is  made,  the  brick  is  first 
thoroughly  dried  and  weighed.  After  soaking,  the  excess  of 
moisture  is  wiped  off  the  surface  and  it  is  weighed  again,  the  per- 
centage of  absorption  being  calculated  in  terms  of  the  original 
dry  weight. 

The  results  obtained  by  the  several  methods  of  testing  are 
well  brought  out  in  a  series  of  tests  made  on  nearly  ninety  dif- 
ferent lots  of  Wisconsin  brick.1 

Three  pairs  of  half  brick  of  each  kind  were  used.  One  pair 
was  completely  immersed  for  48  hours.  A  second  pair  was  half 
immersed  and  its  absorption  measured  at  the  end  of  4  hours  and 
again  after  an  additional  44  hours'  soaking.  A  third  pair  was 
completely  immersed  in  water  under  a  vacuum,  so  that  the 
brick  probably  became  completely  saturated  or  nearly  so. 

In  the  first  of  these  tests,  viz.,  complete  immersion  of  48  hours' 
duration,  the  percentage  of  absorption  ranged  from  5.8  per  cent 
to  34.30  per  cent. 

1  Wis.  Geol.  and  Nat.  Hist.  Surv.,  Bull.  XVI,  1905. 


BUILDING  BRICKS  297 

In  the  partial  immersion  test  it  was  found  that  in  nearly  every 
case  the  brick  at  the  end  of  four  hours  had  absorbed  over  90 
per  cent  of  the  total  quantity  they  were  capable  of  absorbing- 
after  48  hours'  partial  immersion.  The  method  of  manufacture 
and  degree  of  density  did  not  appear  to  affect  the  result  in  any 
way  whatever. 

When  immersed  in  water  under  a  vacuum,  the  percentage  of 
absorption  ranged  from  15.70  per  cent  to  39.90  per  cent,  and,  as 
might  be  expected,  the  amount  of  water  absorbed  was  greatly 
increased,  so  that  the  per  cent  gain  for  any  one  set  ranged  from 
2.3  per  cent  to  69.6  per  cent. 

No  direct  relation  existed  between  the  absorption  and  crush- 
ing strength. 

In  making  an  absorption  test  it  is  better  to  make  it  on  a  half 
brick. 

The  absorption  will  be  less  the  harder  the  brick  is  burned,  but 
this  is  less  noticeable  in  very  sandy  clays.  Repressed  brick  may 
show  a  lower  absorption  than  unrepressed  ones  made  from  the 
same  mixture  and  burned  under  the  same  conditions.  Color 
is  not  necessarily  a  guide  to  the  absorption  power,  except  possibly 
when  comparing  bricks  from  the  same  kiln,  in  which  case  the 
darker  ones,  being  commonly  harder  burned,  may  show  less 
absorption. 

Absorption  and  porosity  are  not  the  same.  Porosity  refers 
to  the  amount  of  pore  space  in  the  brick.  Absorption  is  ex- 
pressed in  percentage  terms  of  the  dry  weight  of  the  brick; 
porosity  is  expressed  in  terms  of  its  volume. 

The  porosity  may  be  determined  by  the  following  simple 

formula  suggested  by  Purdy: 

i(w  —  D}\ 

Percentage  porosity  =  ioo()—- — -)> 

\(W  —  S)  I 

in  which      W  =  saturated  weight, 
D  =  dry  weight, 
S  =  weight  of  brick  suspended  in  water. 

'  The  saturation  may  be  obtained  by  soaking  the  brick  in  water 
in  a  vacuum  or  by  soaking  for  an  hour  in  boiling  water,  the  latter 
method  being  probably  just  as  accurate. 


298 


BUILDING  STONES  AND   CLAY-PRODUCTS 


A  series  of  tests  made  by  J.  C.  Jones,1  indicated  that  the  per- 
centage of  absorption  does  not  bear  any  constant  ratio  to  the 
per  cent  of  porosity. 

The  porosity  of  clay  products  is,  however,  an  important  factor, 
probably,  in  their  durability,  and  certainly  in  their  cleanliness 
and  non-conductivity  of  heat.  If  a  brick  is  very  porous  the 
dirt  will  lodge  in  its  pores  and  spoil  its  appearance,  and  this  ap- 
plies more  strongly  to  some  other  types  of  clay  wares,  as  terra 
cotta. 

While  no  direct  ratio  exists  between  absorption  and  porosity, 
still  we  can  say  that  a  brick  of  high  porosity  will  usually  show 
high  absorption  and  vice  versa. 

A  few  figures  from  Mr.  Jones'  tests  will  illustrate: 


Per  cent  absorption, 
2  weeks'  soaking. 

Per  cent  porosity. 

Ratio  per  cent  ab- 
sorption to  per  cent 
porosity. 

I 

•505 

1.72 

=  3-42 

2 

.576 

2.04 

=  3-54 

23, 

•993 

4.25 

14.28 

3 

i.  08 

2-97 

:2.75 

4 

1.40 

4.56 

13.26 

5 

1-83 

6.26 

••3-42 

6 

2-94 

7.58 

:2-57 

7 

4.28 

10.90 

:2.54 

8 

6.49 

17.0 

12.61 

9 

9.66 

21  .60 

:  2  .  23 

10 

ii  .00 

23-6 

:2.i4 

ii 

11.80 

25.8 

:a.i8 

12 

15.10 

29.  10 

11.92 

Some  rather  extensive  tests  on  absorption  and  porosity  of 
building  brick  by  different  methods  have  been  made  by  Douty 
and  Beebe.2  The  results  of  their  tests  are  given  in  the  following 
table. 

1  Trans.  Amer.  Ceramic  Society,  IX. 

2  "  Some  Further  Experiments  upon  the  Absorption,  Porosity  and   Specific 
Gravity  of  Building  Brick,"  Proceedings  American  Society  for  Testing  Materials, 
Vol.  XI,  p.  767;  see  also  "  The  Influence  of  the  Absorptive  Capacity  of  Bricks  upon 
the  Adhesion  of  Mortar,"  Proceedings  American  Society  for  Testing  Materials, 
Vol.  VIII,  p.  518,  1908;   also,  Howard,  Engineering  News,  Vol.  6,  No.  10,  p.  273, 
March,  1909. 


BUILDING  BRICKS 


299 


COMPARISON  OF  RESULTS  FROM  FIVE  METHODS  OF  DETER- 
MINING ABSORPTION  WITH  WHOLE  AND  HALF  SPECIMENS, 
PREVIOUSLY  DRIED  TO  CONSTANT  WEIGHT  AT  100°  C. 


Partial  immersion  90  days  . 

Total  immersion  90  days. 

Immersion  7  days  and  boil- 
ing I  hour. 

Brick 
No. 

Whole. 

Half. 

Whole. 

Half. 

Whole. 

Half. 

Wt. 

Vol. 

Wt. 

Vol. 

Wt. 

Vol. 

Wt. 

Vol. 

Wt. 

Vol. 

Wt. 

Vol. 

3 

13-4 

25-3 

16.7 

31-6 

13-8 

26.1 

13-9 

26.3 

14.6 

27-6 

15-3 

28.9 

13 

12.  I 

24.4 

12.5 

25-3 

ii.  5 

23.2 

io-5 

21  .  2 

II  .  I 

22.4 

io-S 

21.2 

22 

10.7 

21.7 

10.4 

21  .  I 

10.8 

2!.  9 

n-3 

22.9 

II  .2 

22.7 

IO.  2 

20.7 

2O 

10.6 

21.6 

ii  .0 

22.4 

10.  2 

20.8 

ii  .0 

22.4 

n-5 

23-5 

n-3 

23.1 

21 

9.2 

18.4 

10.7 

21.4 

10.3 

20.  6 

10.3 

20.  6 

II  .0 

22.0 

10.4 

20.8 

8 

8.4 

17.6 

8.9 

I8.7 

10.  I 

21.2 

9-3 

19-5 

8.9 

I8.7 

8-9 

18.7 

18 

8.0 

16.3 

8.0 

I6.3 

7-9 

16.1 

8.1 

16.5 

8.4 

I7.I 

8-3 

16.9 

16 

3-8 

8-4 

4-3 

9-5 

5-i 

ii.  3 

4-9 

10.9 

3-8 

8.4 

5-o 

II  .0 

15 

4.2 

9-7 

3-5 

8.1 

3-6 

8-3 

3-5 

8.1 

6-3 

2-7 

4-7 

10.9 

Aver- 

age . 

18.2 

10.4 

18.8 

18.7 

18.3 

19.  1 

"'fe^ 

*y  •*? 

•*-'  •  O 

Boiling. 

Vacuum. 

Total  immersion  no  days 
and  boiling  4  hours. 

Brick 
No. 

Whole. 

Half. 

Whole. 

Half. 

Whole. 

Half. 

Wt. 

Vol. 

Wt. 

Vol. 

Wt. 

Vol. 

Wt. 

Vol. 

Wt. 

Vol. 

Wt. 

Vol. 

3 

14.0 

26.5 

13.2 

25.0 

I3-I 

24.8 

13-4 

25-3 

14.4 

27.2 

14-3 

27.0 

13 

12.8 

25-9 

12.8 

25-9 

9-7 

19.6 

II  .O 

22.  2 

ii.  9 

24.1 

II  .  I 

22.5 

2 

n-7 

23-8 

II  .2 

22.7 

9.8 

19.9 

io-5 

21-3 

ii.  6 

23.6 

ii.  8 

24.0 

2O 

ii  .  i 

22.6 

II  .2 

22.8 

10.7 

21.8 

10.6 

21  .6 

10.7 

21.8 

n-3 

23.0 

21 

ii  .0 

22.  O 

10.2 

2O.4 

io-5 

21  .O 

10.8 

21.6 

II  .  2 

22.4 

10.9 

21.8 

8 

10.  0 

21  .0 

10.7 

22.5 

9-2 

19-3 

8.0 

16.8 

10.8 

22.7 

9.9 

20.8 

18 

8.5 

17-3 

8.6 

17-5 

7-2 

14-7 

7-2 

14-7 

8.7 

17.7 

8-7 

17.7 

16 

6.0 

13-3 

5-6 

I2.4 

3-o 

6-7 

3-3 

7-3 

6.0 

13.3 

5-7 

12.7 

IS 

4-i 

9-5 

4-2 

9-7 

4.8 

ii  .  i 

3-5 

8.1 

4-9 

H-4 

4-4 

IO.  2 

Aver- 

age.. 

2O.  2 

19.9 

17.7 

17.8 

20.5 

2O.  0 

The  methods  of  making  these  determinations  are  explained 
by  them  as  follows: 

"  Absorption  by  weight  was  obtained  from  the  increase  in 
weight  of  the  specimens  used  in  the  determination  of  the  spe- 
cific gravity  of  normal  brick,  maximum  absorption. 

"  Absorption  by  volume  was  obtained  from  the  product  of  the 
absorption  by  weight  and  the  specific  gravity  of  normal  brick. 


300  BUILDING  STONES  AND   CLAY-PRODUCTS 

It  may  be  observed  that  these  values  approach  very  nearly  the 
values  for  percentage  of  voids.  That  bricks  2  and  16  show 
higher  absorption  by  volume  than  percentage  of  voids  may  be 
ascribed  to  the  fact  that  specimens  from  bricks  with  a  normal 
specific  gravity  higher  than  the  average  were  probably  selected. 
"  Table  III  is  a  comparison  of  the  results  obtained  by  five 
methods  of  determining  absorption  with  both  whole  and  half 
specimens  which  were  previously  dried  to  a  constant  weight  at 

o  /~> 

ioo    C. 

11  In  '  Partial  Immersion  '  the  specimens  were  immersed  to  a 
depth  of  |  inch. 

"In  '  Total  Immersion  '  the  specimens  were  submerged  to  a 
depth  of  \  inch. 

"  In  '  Total  Immersion  and  Boiling/  the  specimens  were  sub- 
merged for  7  days  and  then  boiled  for  i  hour.  All  partial  im- 
mersion tests  were  conducted  under  as  uniform  conditions  of 
air  humidity  and  temperature  as  possible,  i.e.,  ioo  per  cent 
humidity  and  about  68°  F. 

"  In  '  Boiling  '  the  specimens  were  boiled  4  hours  and  weighed 
as  soon  as  cool  enough  to  handle  and  also  24  hours  afterwards. 
In  some  cases  there  was  a  slight  decrease  after  24  hours  and  in 
others  an  increase. 

"In  the  '  Vacuum  Test/  the  specimens  were  subjected  to  a 
reduced  pressure  of  about  68  cm.  of  mercury  for  i  hour  and, 
without  breaking  the  vacuum,  water  was  allowed  to  flow  until 
the  specimens  were  completely  covered  and  then  subjected  to 
a  pressure  of  about  35  Ibs.  for  i  hour. 

"  As  the  table  given  above  is  primarily  a  comparison  of 
methods,  the  averages  of  absorption  may  be  assumed  to  indicate 
the  relative  values  of  these  different  methods." 

Rate  of  Absorption.  —  The  same  authors  also  endeavored  to 
determine  the  rate  of  absorption  for  partial  and  total  immersion 
of  whole  and  half  bricks  by  weight  over  an  extended  period  of  time. 

"At  the  expiration  of  no  days  the  bricks  were  boiled  four 
hours  and  the  percentage  of  absorption  obtained  in  this  way 
was  taken  as  the  maximum  or  ioo  per  cent.  The  percentage 
rate  at  various  periods  was  computed  from  this  maximum. 


BUILDING  BRICKS 


3OI 


"  For  both  whole  and  half  bricks,  it  was  observed  that  ap- 
proximate maximum  absorption  is  attained  at  an  earlier  period 
and  the  rate  of  absorption  is  higher  in  the  case  of  total  immer- 
sion than  partial  immersion,  except  in  a  few  cases  which  can  be 
accounted  for  by  a  variation  in  the  specimens  themselves. 

"Tests  were  made  on  several  of  the  bricks  to  determine  the 
effects  of  repeated  absorption  and  drying.  After  repeating  ab- 
sorption and  drying  ten  times  no  appreciable  change  in  the 
percentage  of  absorption  or  loss  in  weight  could  be  observed." 

Permeability.  —  Tests  on  the  permeability  of  brick  have  been 
made  by  Douty  and  Beebe  l  for  the  purpose  of  determining 
whether  any  relation  exists  between  the  size  or  percentage  of 
voids  and  the  absorptive  capacity.  The  tests  were  made  on 
half  brick  mounted  on  Amsler-Laffon  permeability  apparatus 
and  were  subjected  to  a  pressure  of  about  285  pounds  per  square 
inch.  The  results  of  these  tests  are  given  in  the  following  table. 

RESULTS  OF   PERMEABILITY   TESTS. 


Brick  No. 

Specific  grav- 
ity of  normal 
brick,  dried. 

Specific  grav- 
ity of  ground 
material. 

Voids,  per  cent. 

Permeability, 
cu.  cm.  per  sq. 
cm.  per  min. 

Absorption  by 
volume.percent. 

3 

1.89 

2.66 

28.9 

I  .600 

26.5 

13 

2.02 

2.64 

23-5 

0.500 

21-5 

2 

2.03 

2.6o 

21  .9 

1-957 

22.7 

20 

2.04 

2.65 

22.9 

2  .OOO 

22.8 

21 

2  .00 

2.60 

23.1 

3-230 

21.2 

8 

2.  10 

2.64 

20.5 

0.844 

18.4 

18 

2.04 

2-51 

17.7 

0.570 

17.2 

16 

2  .  22 

2.64 

IO.9 

0.282 

12.4 

15 

2.32 

2.64 

12.1 

0-594 

6.8 

1 

As  stated  in  their  paper  the  data  are  considered  incomplete 
because  they  were  confined  to  a  limited  number  of  specimens 
and  a  comparison  of  the  last  three  columns  of  the  preceding 
table  would  seem  to  indicate  that  the  largest  values  of  permea- 
bility are  obtained  for  those  brick  in  which  the  absorption  by 
volume  nearly  approaches  the  percentage  of  voids. 

1  "  Some  Further  Experiments  upon  the  Absorption,  Porosity  and  Specific  Grav- 
ity of  a  Building  Brick,"  Proceedings  American  Society  for  Testing  Materials, 
Vol.  XI,  p.  767. 


302 


BUILDING   STONES  AND   CLAY-PRODUCTS 


Relation  between  Crushing  Strength,  Transverse  Strength  and 
Absorption.  There  seems  to  exist  a  strong  misconception  on  this 
point. 

The  compressive  strength  cannot  be  correlated  with  the 
absorption,  except  when  such  comparison  is  restricted  to 
samples  of  the  same  clay,  molded  and  burned  under  uniform 
conditions. 

There  is,  as  already  mentioned,  no  definite  relation  between 
the  transverse  and  crushing  strength,  and  this  fact  is  also  brought 
out  in  the  tables. 

A  brick  of  low  transverse  strength  may  be  of  good  crushing 
strength  and  vice  versa. 

The  lack  of  definite  relation  between  the  crushing  strength, 
transverse  strength  and  absorption  is  shown  by  the  following 
figures  taken  from  a  series  of  tests  made  on  a  number  of  Wis- 
consin brick. 


Kind  of  brick. 

Average  crush- 
ing strength. 

Average  modu- 
lus of  rupture. 

Per  cent  ab- 
sorption. 

Soft  mud  

IIO2 

526 

2O   ?,Z 

Soft  mud 

AC72 

s6o 

14-   4- 

Soft  mud 

3036 

1063 

18  7 

Soft  mud  

C7o6 

1062 

22    2< 

Stiff  mud  
Stiff  mud  

1540 
2708 

588 

crco 

34.3 

27  .6 

Stiff  mud  

2234 

IOQ7 

24.  15 

Stiff  mud 

4006 

IOQO 

20  8q 

Stiff  mud 

I^4O 

588 

2A     2 

Stiff  mud  

^IIO 

2IQO 

Soft  mud  
Soft  mud 

1192 

4-^72 

526 

e6o 

24.65 
14  4 

Fire  Tests.  Freitag 1  states  that  "  many  fires  have  fully 
demonstrated  the  fire-resisting  qualities  of  good  brickwork.  Its 
ability  to  withstand  fire  and  water  tests  depends  on:  (a)  the 
method  of  manufacture,  (b)  the  chemical  properties  of  the  ma- 
terials employed,  (c)  the  method  of  use. 

"  Both  the  Baltimore  and  San  Francisco  fires  demonstrated 
that  good  quality  brickwork,  used  for  walls  or  column  casings, 
suffered  less  than  any  other  material. 

1  "  Fire  Prevention  and  Fire  Protection,"  p.  219. 


BUILDING  BRICKS  303 

"  Ordinary  well-burned  brick  of  good  quality  is  the  most 
satisfactory  fire-resisting  material  now  used  in  building  con- 
struction. When  the  walls  were  laid  with  hard  brick,  with 
plenty  of  headers  and  in  portland  cement  mortar,  and  were 
properly  tied  to  the  floor  and  roof  members,  there  was  little  if 
any  damage." 

A  fire  test  of  brick  is  of  great  importance. 

When  such  a  test  is  made,  it  is  customary  to  heat  a  sample 
of  the  brick  to  redness  in  a  furnace  and  then  plunge  it  into  cold 
water.  This  may  be  satisfactory  if  no  other  means  is  at 
hand. 

A  far  better,  though  expensive,  plan  is  that  formerly  followed 
in  the  fire-testing  station  of  Columbia  University,  under  the 
direction  of  Professor  I.  A.  Woolson. 

A  house  was  constructed  with  exterior  dimensions  of  14  feet 
6  inches  by  9  feet  6  inches,  consisting  of  reinforced  concrete  walls 
and  roof,  while  the  side  walls  were  removable.  The  floor  of  the 
building  is  a  grate  upon  which  the  fire  is  built  and  suitable  draft 
openings  and  chimneys  are  provided.  The  sides  were  built  as 
8-inch  walls  of  the  brick  to  be  tested. 

The  brick  were  laid  in  bands  about  14  inches  wide,  in  order 
that  each  variety  of  brick  might  be  subjected  to  the  same  heat, 
and  as  far  as  possible  only  half  a  band  was  laid  on  the  same  level 
in  the  wall;  the  other  half  was  placed  in  some  other  position. 
The  purpose  of  the  test  is  to  determine  the  effect  of  a  continuous 
fire  against  the  walls  for  two  hours,  bringing  the  heat  up  slowly 
to  1700°  F.  during  the  first  half  hour  and  maintaining  this  as 
nearly  as  possible  during  the  remainder  of  the  test.  Then  a 
one  and  one-eighth-inch  stream  of  cold  water  was  thrown  against 
the  wall  for  three  minutes  at  hydrant  pressure,  which  varied  from 
25  to  30  pounds. 

In  one  test  several  large  cracks  developed  in  the  walls  and  the 
brick  themselves  were  full  of  cracks.  Indeed,  it  was  very  difficult 
to  get  a  whole  brick.  In  general,  the  brick  were  affected  by  the 
fire  about  half  way  through.  Samples  of  the  brick  tested  for 
their  crushing  strength  after  the  fire  test  showed  in  nearly  every 
case  a  marked  decrease. 


304  BUILDING   STONES  AND   CLAY-PRODUCTS 

A  testing  furnace1  in  use  at  the  Underwriters'  Laboratory  of 
Chicago  consists  of  a  gas  furnace  with  "  a  movable  steel  frame 
fire-brick  wall  or  door  14  inches  thick  that  shuts  off  the  furnace 
from  a  radiation  chamber."  .  .  .  "This  movable  wall  has  an 
arched  opening  6  feet  wide  and  9  feet  high.  The  material  to 
be  tested  is  built  up  in  this  opening  as  a  panel." 

After  the  panel  is  filled  and  shoved  into  place,  the  fire  chamber 
is  heated  by  gas.  An  effort  was  made  to  obtain  the  maximum 
temperature,  1700°  F.,  within  one-half  hour  after  starting  the 
test,  and  to  maintain  this  temperature  as  nearly  constant  as 
possible  for  two  hours.  At  the  end  of  this  time  the  panel  con- 
taining test  brick  was  pulled  out  and  a  stream  of  water  from  a 
1-inch  nozzle  at  50  pounds  pressure  directed  against  the  hot 
surface  for  a  period  of  five  minutes. 

These  conditions  were  unusually  severe,  and  the  temperatures 
were  those  not  usually  reached  in  an  actual  fire. 

Much  of  the  damage  done  was  due  to  internal  stresses,  be- 
cause gas  flame  of  the  furnace  heated  one  face  more  rapidly  than 
the  other  face. 

Many  of  the  materials  were  poor  non-conductors  of  heat,  the 
natural  building  stones  and  tiles  proving  specially  bad  in  this 
respect.  This  naturally  set  up  stresses  which  the  webs  of 
ordinary  hollow  blocks  were  insufficient  to  resist. 

Brick  panels  withstood  tests  better  than  other  materials 
and  comprised  unused  new  Chicago  brick  and  used  St.  Louis 
brick.  Fifty  per  cent  of  the  new  brick  were  split,  while  60  to 
70  per  cent  of  the  old  brick  were  not  damaged.  Lime  knots 
apparently  caused  damage.  The  bricks  at  back  of  panels  were 
unaffected. 

Hydraulic  pressed  brick  stood  the  test  very  well  and  70  per 
cent  were  found  sound  after  quenching. 

The  tile  tested  behaved  badly.  One  was  a  hollow-glazed 
building  tile,  8  by  8  by  16  inches,  with  ^-inch  web  and 
four  core  holes  running  throughout  its  length.  The  other, 
a  partition  tile,  5  by  12  by  12  inches,  with  a  f-inch  web,  .and 
three  core  holes. 

1  U.  S.  Geol.  Survey,  Bull.  370. 


BUILDING  BRICKS 


305 


Unfortunately,  no  detailed  and  conclusive  series  of  tests  have 
been  made  to  determine  the  relative  fire  resistance  of  brick  made 
by  different  methods. 

Vitrified  bricks  will  usually  spall  badly  when  subjected  to  fire 
and  water  treatment.  Stiff-mud  brick,  if  at  all  laminated,  show 
a  tendency  to  split  off  along  the  planes  of  lamination.  And  yet, 
brick  will  on  the  whole  stand  fire  better  than  most  building 
stones. 

Coefficient  of  Expansion.  The  following  tests  of  coefficients  of 
expansion  of  burned  clay  wares  is  of  interest  in  this  connection. 
These  tests  were  made  at  the  Watertown  Arsenal,1  the  brick 
being  heated  in  a  hot- water  bath. 

COEFFICIENTS  OF  EXPANSION  OF  BRICKS,  AS  DETERMINED 
IN  WATER  BATHS. 


Character  of  product. 

Original 
gauged 
length  in 
air. 

Hot. 

Cold. 

Differ- 
ence. 

Difference 
in  length. 

Coefficient  of 
expansion. 

Red  brick,  No.  i  
Red  brick,  No.  2  
Red  brick,  No.  3  
Red  brick,  No.  4  
Fire  brick,  No.  i  
Fire  brick,  No.  2  
Hollow  fireproof 
building  brick 

6.0852 
6.OIOQ 
5-9396 
6.0204 
5.9968 
5.9988 

10  0036 

X  00  00  00  00  00  OO 

34 
34 
34 
34 
34 
34 

T.A 

O  O  O  O  O  O  H 

IO  IO  IO  f>  IO  vr>  H 

.0032 
.0023 
.0023 
.0029 
.0026 
.0022 

OO44 

.00000351 
.00000255 
.00000258 
.00000321 
.00000289 
.00000244 

00000291 

Frost  Test.  There  is  no  universally  accepted  standard  method 
of  making  this  test. 

Some  engineers  take  either  a  whole  or  half  brick,  soak  it 
thoroughly  in  water  from  two  to  even  five  days,  and  then  put  it 
in  a  refrigerating  chamber  where  it  is  exposed  to  a  freezing  tem- 
perature for  perhaps  23  hours,  followed  by  one  hour  thawing  at 
a  temperature  of  about  i2o°F.  This  process  is  repeated  pref- 
erably about  twenty  times  and  the  loss  in  weight  or  evidence  of 
disintegration  noted. 

The  work  of  the  Iowa  Geological  Survey  on  bricks  from  that 
state2  has  shown  that  rough  Cubes  when  subjected  to  the  freezing 

1  Tests  of  Metals,  etc.,  1890. 

2  Iowa  Geological  Survey,  XIV. 


306  BUILDING  STONES  AND   CLAY-PRODUCTS 

test  gave  greater  losses  than  smoother  and  larger  ones  respec- 
tively. Their  conclusions  were  based  on  20  hours'  freezing  and 
4  hours'  thawing,  repeated  thirty  times. 

It  has  been  noticed1  that  the  method  of  placing  bricks  in  a 
freezing  box  may  also  cause  difference  in  the  results. 

Thus,  if  the  brick  are  placed  close  together,  the  evaporation 
that  takes  place  from  the  surface  of  a  warm  brick  when  placed 
in  the  refrigerating  chamber  is  retarded.  More  water  remains 
in  the  pores,  and  the  brick  will  be  more  damaged.  If  the  same 
brick  are  separated  when  placed  in  the  freezing  box,  a  lower 
percentage  of  loss  or  disintegration  occurs.  This  fact  was  dis- 
covered by  the  different  reports  made  by  two  laboratories,  in 
testing  brick  of  the  same  make.  The  one  in  which  the  brick 
were  frozen  in  a  closely  set  position  reported  a  far  greater  loss. 

There  is  some  doubt  as  to  what  are  the  causes  governing  the 
frost  resistance  of  brick,  but  the  common  idea  is  that  the  harder 
burned  a  brick  the  greater  its  frost  resistance.  This  theory  is 
based  on  the  fact  that  with  increased  hardness  of  burning,  there 
is  an  increase  in  strength  and  decrease  in  pore  space.  It  is 
claimed  by  some,  however,  that  freezing  tests  on  brick  do  not 
bear  this  out;  moreover,  the  crushing  strength  of  some  of  the 
hardest  brick  is  most  affected  by  freezing. 

Of  course,  the  degree  to  which  a  given  brick  is  affected  will 
depend  to  a  certain  extent  upon  its  degree  of  saturation. 

If  the  pores  are  not  completely  filled  with  water  there  may  be 
room  for  the  latter  to  expand  in  freezing  without  exerting  any 
internal  pressure,  while  if  the  pores  are  filled,  then,  unless  the 
water  can  force  its  way  out  in  freezing,  considerable  internal 
pressure  may  develop. 

Jones2  suggests  that  the  power  of  a  brick  to  withstand  frost 
action  depends  on  the  amount  of  pore  space,  the  rate  at  which 
water  can  flow  through  the  pores,  and  the  crushing  strength. 

A  very  porous  brick  may  drain  more  easily,  provided  the  pores 
are  large  and  straight,  so  that  some  of  the  water  may  drain  off 
before  freezing.  If  the  pores  are  tortuous,  the  water  may  not 

1  Tonindustrie  Zeitung,  XXXII,  p.  1846,  1908. 

2  Trans.  Amer.  Ceramic  Society,  IX,  p.  528,  1907. 


BUILDING  BRICKS  307 

only  drain  off  more  slowly,  but,  if  it  freezes,  remain  within  the 
brick. 

The  crushing  strength  may  indicate  the  relative  resistance 
which  a  brick  will  offer  to  the  expansive  force  of  freezing  water. 

Hard-burned  brick  have  greater  strength  and  greater  rigidity 
than  soft-burned  ones,  and  while  they  have  a  smaller  pore  space, 
and  have  less  water  when  filled,  still  they  drain  more  slowly,  and, 
though  having  greater  strength  to  resist  expansion,  will  rupture 
with  less  expansion.  A  given  amount  of  expansion  on  freezing 
might,  therefore,  rupture  a  rigid  brick,  when  it  would  not  harm 
a  more  elastic  or  a  tougher  one. 

If  brick  are  to  be  used  in  the  foundation  where  they  are  liable 
to  be  exposed  to  moisture  it  is  best  to  use  those  of  high  crushing 
strength  and  low  porosity. 

Proposed  Standard  Specifications  for  Building  Brick.  The 
following  have  been  proposed  by  the  American  Society  for 
Testing  Materials.1 

Selection  of  Samples.  For  the  purpose  of  tests,  brick  shall 
be  selected  by  some  disinterested  and  experienced  person  to 
represent  the  commercial  product.  All  brick  shall  be  carefully 
examined,  and  their  condition  noted  before  being  subjected  to 
any  test. 

Transverse  Test.  At  least  five  brick  shall  be  tested,  laid  flat- 
wise with  a  span  of  7  inches,  and  with  the  load  applied  at  mid- 
span.  The  knife  edges  shall  be  slightly  curved  in  the  direction 
of  their  length.  Steel  bearing  plates,  about  J  inch  thick  and 
ij  inches  wide,  may  be  placed  between  the  knife  edges  and  the 
brick.  The  use  of  a  wooden  base-block,  slightly  rounded  trans- 
versely across  its  top,  upon  which  to  rest  the  lower  knife  edges, 
is  recommended.  The  modulus  of  rupture  shall  be  obtained 
by  the  following  formula: 


in  which  e  is  the  distance  between  supports  in  inches,  b  is  the 
breadth  and  d  the  depth  of  the  brick  in  inches,  and  W  is  the 
load  in  pounds  at  which  the  brick  failed. 

1  Vol.  IX,  p.  131. 


308  BUILDING  STONES  AND   CLAY-PRODUCTS 

The  half  bricks  resulting  from  the  transverse  test  shall  be 
used  for  the  compression  and  absorption  tests.  One  half  shall 
be  crushed  in  its  dry  condition;  the  other  half  shall  be  used  for 
the  absorption  test  and  crushed  while  in  its  wet  condition.  No 
specimen  shall  be  used  if  any  part  of  the  line  of  fracture  is  more 
than  i  inch  from  the  center  line. 

Compression  Test.  Compression  tests  shall  be  made  on  half 
brick  resulting  from  the  transverse  test.  The  brick  shall  be 
bedded  flatwise  on  blotting  paper,  heavy  fibrous  building  paper 
or  heavy  felt,  to  secure  a  uniform  bearing  in  the  testing  machine. 
In  case  the  brick  have  uneven  bearing  surfaces,  they  shall  be 
bedded  in  a  thin  coat  of  plaster  of  Paris.  For  the  dry  test,  before 
applying  the  plaster  of  Paris,  the  bearing  surfaces  of  the  brick 
shall  receive  a  coat  of  shellac.  The  machine  used  for  compres- 
sion tests  shall  be  equipped  with  spherical  bearing  blocks.  The 
breaking  load  shall  be  divided  by  the  area  in  compression,  and 
the  results  reported  in  pounds  per  square  inch. 

Absorption  Test.  At  least  five  half  brick  shall  be  first  thor- 
oughly dried  to  constant  weight,  at  a  temperature  of  from  200° 
to  250°  F.,  weighed,  and  then  placed  on  their  face  in  water  to  a 
depth  of  i  inch  in  a  covered  container.  The  brick  shall  be 
weighed  at  the  following  intervals :  one-half  hour,  six  hours,  and 
forty-eight  hours.  Superfluous  moisture  shall  be  removed  before 
each  weighing.  The  absorption  shall  be  expressed  in  terms  of 
the  dry  weight,  and  the  balance  used  must  be  accurate  to  5  grams. 

Freezing  and  Thawing  Tests.  In  case  the  freezing  and  thawing 
test  is  desired,  at  least  five  brick  shall  be  thoroughly  saturated 
by  immersion  in  cold  water,  which  shall  be  raised  to  200°  F.  in 
thirty  minutes,  and  then  allowed  to  cool.  The  specimen  shall 
be  immersed  in  ice  water  for  not  less  than  one  hour,  weighed, 
then  transferred  to  the  refrigerator  and  supported  in  such  a 
manner  that  all  faces  will  be  exposed.  The  specimen  shall  be 
subjected  to  a  temperature  of  less  than  15°  F.  for  at  least  five 
hours,  then  removed  and  placed  in  water  at  a  temperature  of 
not  less  than  150°  F.,  nor  more  than  200°  F.,  for  one  hour.  This 
operation  shall  be  repeated  twenty  times,  after  which  the  brick, 
still  saturated,  shall  be  weighed  again.  The  character  of  the 


BUILDING  BRICKS 


3°9 


brick  shall  be  noted  before  and  during  the  test,  and  all  visible 
changes  recorded.  Immediately  on  completion  of  this  test,  the 
samples  are  to  be  thoroughly  dried  and  subjected  to  the  trans- 
verse and  compression  tests. 

Requirements.     The    following    requirements    shall    be    met. 
The  modulus  of  rupture  shall  be  as  follows: 


Average, 
Ibs. 

Minimum. 

For  samples  thoroughly  dry 

AOO 

•22*; 

For  samples  thoroughly  saturated  
For  samples  subjected  to  freezing  and  thawing 
process                            

275 
27^ 

225 
22Z 

The  ultimate  compression  strength  shall  be  as  follows: 


Average, 
Ibs.  per  sq.  in. 

Minimum, 
Ibs.  per  sq.  in. 

For  samples  thoroughly  dry  

3000 

2SOO 

For  samples  thoroughly  saturated 

2<OO 

2QOO 

For  samples  subjected  to  freezing  and  thawing 
process 

2<OO 

2OOO 

The  absorption  shall  not  average  higher  than  15  per  cent, 
and  in  no  case  shall  it  exceed  20  per  cent. 

The  freezing  and  thawing  tests  shall  not  cause  cracking  or 
serious  spalling  in  any  of  the  brick  tested,  nor  cause  serious 
disintegration  of  the  material. 

Specific  Gravity.  The  specific  gravity  of  a  brick  is  some- 
times considered  in  connection  with  other  tests  upon  its  quali- 
ties, but  comparatively  few  data  have  been  published  upon 
this  matter.  Recently  Douty  and  Beebe  1  made  some  deter- 
minations on  the  specific  gravity  of  ground  material,  as  well  as 
of  the  normal  brick.  For  this  purpose  four  samples  covering  a 
range  of  variation  were  selected  and  the  specific  gravity  of  the 
ground  material  passing  different  sizes  of  sieves  was  obtained. 
Brick  samples  were  first  crushed  to  pass  a  number  20  sieve, 

1  "  Some  Further  Experiments  upon  the  Absorption,  Porosity  and  Specific 
Gravity  of  a  Building  Brick,"  Proceedings  American  Society  for  Testing  Materials, 
Vol.  XI,  p.  767. 


3io 


BUILDING   STONES   AND   CLAY-PRODUCTS 


thoroughly  mixed  and  then  divided  into  .portions  to  be  subse- 
quently crushed  to  pass  sieves  of  40,  60,  80,  100  and  200  mesh. 
These  determinations  were  made  with  a  Le  Chatelier  flask  after 
all  moisture  had  been  driven  off  and  the  results  of  the  tests  are 
given  in  the  table  below. 

COMPARISON   OF  THE   SPECIFIC  GRAVITIES   OF    GROUND 

MATERIAL  TO   PASS  DIFFERENT  SIZES  OF   SIEVES. 

Le  Chatelier  Flask. 


Sieve  number. 

Brick  No. 

20 

40 

60 

80 

100 

200 

2 

2.568 

2  .  590 

2.6OO 

2.604              2.6l3 

2.636 

18 

2-457 

2.4QO 

2.506 

2.522 

2-533 

2-547 

10 

2.462 

2.510 

2.538 

2-545 

2.552 

2.580 

13 

2.582 

2.626 

2.644 

2.648 

2.659 

2.689 

Pyknometer. 


18 

2-433 

2.487 

2.517 

2-527 

2-534 

2-550 

A  series  of  check  determinations  on  brick  was  made  with  the 
pyknometer  and  reference  to  the  table  shows  that  there  is  a 
marked  increase  in  the  value  of  the  specific  gravity  up  to  number 
60  sieve.  In  subsequent  comparisons,  therefore,  the  specific 
gravity  of  the  ground  material  passing  through  a  number  60 
sieve  was  used  by  them  as  a  basis. 

COMPARISON  OF  THE  SPECIFIC  GRAVITIES  OF  NINE  BRICKS 
WITH  ABSORPTION   BY  THE  BOILING  METHOD. 


Brick  No. 

Specific  gravity 
of  ground 
material. 

Specific  gravity 
of  normal 
brick,  maxi- 
mum absorp- 
tion. 

Specific 
gravity  of 
normal 
brick,  dried. 

Voids,1  per 
cent. 

Absorption 
by  weight, 
per  cent. 

Absorption 
by  volume, 
per  cent. 

3 

2.66 

2.64 

1.89 

28.9 

14.02 

26.5 

13 

2.64 

2.64 

2.  O2 

23-5 

10.62 

21-45 

2 

2.60 

2.61 

2.03 

21.9 

II  .  20 

22.7 

20 

2.05 

2.62 

2.O4 

22.9 

II  .20 

22.8 

21 

2.60 

2.58 

2.OO 

23.1 

10.62 

21.2 

8 

2.64 

2.59 

2.  IO 

20.5 

8.78 

18.4 

18 

2.51 

2.48 

2.O4 

17.7 

8.45 

17.2 

16 

2.64 

2.58 

2.22 

IO.9 

5.60 

12.4 

15 

2.64 

2.53 

2.32 

12.  I 

2.95 

6.8 

Percentage  of  voids 


Specific  gravity  of  normal  brick,  dried 

100 g r^-   — r: f —  r-r-r    X  IOO. 

Specific  gravity  of  ground  material 


BUILDING  BRICKS  311 

In  the  preceding  table  there  are  given  the  specific  gravities 
of  nine  bricks  together  with  their  absorption  by  the  boiling 
method. 

To  quote  further  from  them: 

"  The  specific  gravity  of  normal  brick,  maximum  absorption, 
was  obtained  by  boiling  quarter  portions  of  the  samples  for  4 
hours  in  hydrant  water  and  determining  the  specific  gravity  by 
the  method  of  suspension  in  distilled  water,  correction  being 
made  for  the  higher  specific  gravity  of  water  absorbed.  As 
may  be  noticed,  the  values  in  this  column  very  nearly  approach 
the  values  for  the  specific  gravity  of  ground  material  and 
would  probably  equal  them  if  maximum  absorption  had  been 
obtained. 

uThe  specific  gravity  of  normal  brick  dried  was  obtained  by 
drying  quarter  portions  of  the  brick  to  constant  weight,  coating 
with  shellac  varnish  and  baking  in  an  oven  at  approximately 
215°  F.  until  hard,  repeating  the  process  of  coating  and  baking 
until  the  absorption  was  so  slight  as  to  not  materially  affect  the 
values  obtained  by  the  suspension  method.  The  specific  gravity 
of  the  shellac  was  found  to  be  1.067  and  a  correction  made  to 
allow  for  the  coating. 

"The  ratio  of  the  specific  gravity  of  the  normal  brick  dried  to 
the  specific  gravity  of  the  ground  material,  multiplied  by  100, 
expresses  the  percentage  of  solid  matter  present  in  the  normal 
brick;  this  subtracted  from  100  per  cent  gives  the  percentage 
of  voids. 

"  Absorption  by  weight  was  obtained  from  the  increase  in 
weight  of  the  specimens  used  in  the  determination  of  the  spe- 
cific gravity  of  normal  brick,  maximum  absorption. 

"  Absorption  by  volume  was  obtained  from  the  product  of  the 
absorption  by  weight  and  the  specific  gravity  of  normal  brick. 
It  may  be  observed  that  these  values  approach  very  nearly  the 
values  for  percentage  of  voids.  That  bricks  2  and  16  show 
higher  absorption  by  volume  than  percentage  of  voids  may  be 
ascribed  to  the  fact  that  specimens  from  brick  with  a  normal 
specific  gravity  higher  than  the  average  were  probably 
selected." 


312  BUILDING  STONES  AND   CLAY-PRODUCTS 

Efflorescence  or  Scum  on  Brick.1  Many  brick  after  being  set 
in  the  wall  develop  an  unsightly  white  scum,  while  on  others 
it  may  show  before  it  leaves  the  factory.  This  stain  can  often 
be  prevented  if  brickmakers  and  builders  take  the  proper 
precautions. 

It  is  without  doubt  more  or  less  unsightly  and  may  harm  the 
brick. 

In  view  of  all  this  it  is  well  for  the  architect  to  know  something 
of  the  cause  of  this  efflorescence  and  methods  of  preventing  it. 

The  scum  is  due  to  the  presence  of  soluble  compounds  such 
as  sulphates  of  lime,  magnesia,  potash,  or  soda,  in  the  burned 
or  unburned  clay,  which  are  brought  to  the  surface  when  the 
water  in  the  ware  evaporates. 

The  causes  of  efflorescence  are  classified  by  Gunther2  as  follows: 

I.   Efflorescence  from  causes  due  to 

1.  Raw  clay. 

2.  Water  used  in  tempering. 

3.  Firing,  and  caused  by 

a.  Ingredients  of  the  coal  ash. 

b.  Sulphur  in  the  coal. 

c.  Pyrite  in  the  clay. 

II.   Efflorescence  from  mortar  due  to 

1.  Infiltration  of  soluble  salts  into  the  brick. 

2.  Chemical  reactions  between  the  alkalies  of  the  mortar 

and  lime  sulphate  in  the  clay. 

Efflorescence  due  to  the  raw  clay  or  water  used  for  mixing 
forms  on  the  surface  of  the  ware  during  the  drying  process,  so 
that  bricks  coming  from  a  dryer  sometimes  show  this  white  scum 
very  clearly.  This  may  be  termed  dryer  white.  When  due  to 
the  clay,  the  soluble  salts  may  be  primary  constituents  of  the 
clay  and  removable  by  leaching,  or  they  may  develop  in  the 
clay  if  the  latter  is  exposed  to  the  weather  for  any  length  of  time. 

1  References  on  Scumming.     Seger's  collected  writings.     Gunther,  Baumaterial- 
ienkunde,  XXIV  and  XXV,  p.  385;   also  Tonindustrie  Zeitung,  XXX,  p.  583; 
Gerlach,  Brickbuilder,  1899;  J.  C.  Jones,  Trans.  Amer.  Ceramic  Society,  VIII 
p.  369;  E.  Lovejoy,  Trans.  Amer.  Ceramic  Society,  VIII,  p.  255,  1906 

2  Baumaterialienkunde,  1896-97,  p.  385. 


BUILDING  BRICKS  313 

The  preventive  methods  consist  of  (i)  using  un weathered 
clay,  (2)  removing  soluble  salts  present  by  leaching,  if  possible, 
(3)  by  adding  chemicals  such  as  barium  chloride  or  carbonate 
which  will  convert  them  into  an  insoluble  form. 

Kiln  white  is  chiefly  lime  sulphate,  formed  by  the  action  of  the 
sulphurous  gases  of  the  fuel  on  lime  in  the  clay,  or  by  the  oxida- 
tion of  iron  sulphide  to  iron  sulphate,  which  is  soluble. 

It  may  become  burned  into  the  brick  and  be  difficult  of 
removal. 

Wall  white  is  a  scum  which  forms  on  a  brick  wall  and  can  be 
rubbed  off. 

It  appears  to  consist  mostly  of  sulphates  of  lime  and  magnesia, 
but  soda  and  potash  sulphates  may  also  be  present. 

Wall  white  may  be  caused  by  soluble  salts  contained  within 
the  brick,  or  it  may  come  from  the  mortar  or  even  the  mortar 
color.  If  from  the  mortar,  it  may  be  due  to  carbonates  of  mag- 
nesia, soda  or  potash  washed  out  of  the  cement,  reacting  with 
lime  suphate  in  the  brick,  forming  lime  carbonate,  which  is  quite 
insoluble  and  remains  in  the  brick,  while  the  magnesium,  sodium 
or  potash  sulphates  formed  are  carried  to  the  surface. 

The  remedies  for  wall  white  are  to  make  the  walls  as  imper- 
vious to  water  as  possible,  or  use  well-burned  brick  and  coat 
the  foundations  with  waterproof  paint. 

Painting  a  wall  after  the  scum  has  appeared  is  often  productive 
only  of  temporary  improvement,  as  the  scum  and  paint  may 
peel  off. 

Testing  Brick  for  Scumming  Power.  There  is  no  standard 
method  of  testing  this,  but  the  following  is  suggested  byMackler.1 
Experiments  made  by  him  showed  that  gypsum  was  not  the  sole 
cause  of  scumming.  Brick  with  i  per  cent  of  gypsum  might 
not  scum,  while  others  with  but  0.03  per  cent  of  sulphates  of 
potash,  soda  or  magnesia  might  do  so. 

The  test  for  determining  the  scumming  power  consisted  of 
placing  the  brick  on  two  glass  rods  over  a  shallow  dish. 

A  bottle  of  distilled  water  was  fastened  in  an  inverted  position 
to  the  upper  surface  of  the  brick,  which  thus  absorbed  the  water. 

1  Tonindustrie  Zeitung,  1905. 


314  BUILDING  STONES  AND   CLAY-PRODUCTS 

The  latter  passed  through  the  brick,  dissolved  the  soluble  salts 
and  brought  them  to  the  surface. 

Experiments  showed  that  the  scumming  was  not  always  pro- 
portional to  the  amount  of  soluble  salts  present,  so  tests  were 
made  to  determine  the  effect  of  different  salts  when  the  brick 
were  burned  at  different  temperatures. 

Small  amounts  of  lime  and  potash  sulphates  showed  no  bad 
effects,  but  as  little  as  o.oi  per  cent  of  sodium  or  magnesium 
sulphate  produced  a  scum. 

Brick  which  were  fired  in  an  oxidizing  atmosphere  showed 
slightly  more  efflorescence  than  those  burned  in  a  reducing 
fire. 

The  densest  brick  showed  the  most  efflorescence,  but  the  size 
of  the  pores  seemed  to  be  a  factor  in  preventing  scumming. 

Scumming  of  a  brick  or  other  piece  of  clay  ware  might  be 
tested  by  placing  the  object  partially  immersed  in  a  dish  of 
water,  protected  from  dust,  and  allowing  it  to  remain  there. 
The  water  is  drawn  in  through  the  sides  of  the  piece  and  evapo- 
rates from  the  top,  carrying  the  soluble  salts  with  it. 

Requisite  Qualities  of  Brick.  There  may  be  a  wide  divergence 
of  opinion  as  to  what  should  constitute  a  good  brick,  but  the 
author  would  venture  to  suggest  the  following. 

Common  Brick.  Color  preferably  red.  Sufficiently  hard 
burned  to  give  a  good  ring  when  struck  together.  Not  neces- 
sarily steel  hard.  Freedom  from  lime  pebbles.  Absorption 
preferably  not  over  15  per  cent,  but  a  good  brick  may  show 
more.  Crushing  strength  not  less  than  2000  pounds  per 
square  inch.  Modulus  of  rupture  preferably  not  under  300 
pounds.  If  stiff-mud,  freedom  from  laminations.  Good  frost- 
resisting  qualities. 

Pressed  Brick.  Steel  hard  if  possible.  Freedom  from  lime 
pebbles  and  soluble  salts.  Crushing  and  transverse  strength  at 
least  as  high  as  in  common  brick,  but  is  usually  much  better. 
Absorption  preferably  low.  For  certain  purposes  smoothness  of 
surface,  sharpness  of  corners  and  straightness  of  edges  are  de- 
manded. Indeed,  exactness  of  form  and  outline  represent  the 
attainment  of  a  high  degree  of  mechanical  perfection. 


mflini 


O    ^— ^ 

12 


i  -2 

I-H     3 


BUILDING  BRICKS  317 

In  the  early  years  of  the  pressed-brick  industry,  the  product 
exhibited  a  great  monotony  of  color  and  the  smooth  red  brick 
front  was  the  rule. 

In  recent  years,  however,  there  has  been  a  marked  change, 
and  facing  bricks  are  now  made  in  buff,  white,  gray,  speckled, 
tan,  old  gold,  white,  black,  green,  etc. 

The  production  of  this  variety  in  colors  is  due  in  part  to  proper 
selection  and  understanding  of  the  raw  material,  but  also  to 
technical  skill  in  handling  the  burning. 

Of  equal  interest  is  the  recent  tendency  to  depart  from  the 
smooth  surface  front  brick,  set  with  narrow  mortar  joints,  and 
to  select  instead  a  rougher  faced  product,  set  in  thick  mortar 
seams.  Absolute  uniformity  of  shade  in  the  same  wall  face  is 
also  objected  to  by  many  architects. 

It  is  no  doubt  true  that  there  is  here  a  gain  in  both  structural 
and  decorative  effect. 

A  recent  development  in  artistic  brickwork  is  known  as 
"  Brickotta  "  (Plate  LI).  It  is  a  form  of  terra  cotta,  which  is 
hand  mok}ed  and  hand  finished,  being  divided  into  units  corre- 
sponding approximately  to  brick  sizes.  It  is  made  of  the  same 
color  and  texture  as  the  surrounding  brickwork. 

Enameled  Brick.  The  bricks  may  be  made  on  stiff-mud  or 
soft-mud  machines,  and  repressed,  or  in  a  dry  press. 

They  are  then  usually  dipped  by  hand  in  a  slip,  which  shows 
the  desired  color  after  burning,  and  then  a  glaze  is  applied  over 
the  slip. 

At  one  works  an  automatic  veneering  process  is  used,  which 
consists  in  having  a  special  device  attached  to  the  die  of  a  stiff- 
mud  machine,  so  that  the  slip  is  spread  on  the  column  of  clay  in 
a  thin  layer  as  it  issues  from  the  machine. 

Enameled  bricks  are  usually  burned  in  one  firing,  following  the 
application  of  the  slip  and  glaze,  but  in  some  cases  the  brick  may 
be  burned  before  slipping,  and  then  receive  a  second  firing  after 
the  application  of  slip  and  glaze.  The  two-fire  method  increases 
the  cost  of  manufacture. 

Defects  in  the  enamel,  such  as  pinholes,  cracks,  etc.,  may  be 
caused  by  improper  preparation  of  the  slip,  bad  dipping,  etc.; 


318  BUILDING  STONES  AND  CLAY-PRODUCTS 

crazing,  cracking  and  scaling  of  the  enamel  may  also  be  the 
result  of  improper  composition  of  body  and  slip,  etc. 

The  enameled  brick  formerly  manufactured  were  chiefly  of 
white  color,  but  now  a  variety  of  colors  are  made,  and  the  prod- 
uct, although  first  obtained  exclusively  from  abroad,  is  now  made 
at  a  number  of  localities  in  the  United  States. 

Two  sizes  are  recognized,  viz.,  the  English  (9  by  4!  by  3  inches) 
and  the  American  (8f  by  4!  by  2§  inches). 

A  good  brick  should  have  an  enamel  which  is  smooth,  free 
from  pinholes  or  bubbles  and  crazing.  The  last  does  not  at 
times  appear  until  the  brick  has  been  in  use  for  several 
months. 

Enameled  brick  were  formerly  made  only  with  a  full-glazed 
surface,  but  now  matt  glazes  and  semi-lustrous  glazes  are  also 
made. 

Where  enameled  brick  are  used  in  damp  situations,  they  un- 
fortunately show  a  tendency  to  flake  off  after  the  course  of  a  few 
years. 

The  agencies  likely  to  work  injury  to  an  enameled  brick  are: 
Frost,  crystallization  of  soluble  compounds  in  the  brick,  corrosive 
liquids  or  vapors,  pressure,  change  of  temperature,  scouring 
action  and  percussion. 

There  are  no  standard  methods  for  testing  enameled  bricks, 
but  the  following  ones  have  been  suggested: 

1.  Immerse  the  brick,  enameled  face  down,  to  a  depth  of  one 
inch  in  a  hot,  saturated  solution  of  brine.     After  soaking,  remove 
and  cool,  repeating  the  treatment  a  number  of  times.     A  poor 
brick  may  craze  after  i  or  2  soakings,  while  a  good  one  will  stand 
this  treatment  at  least  5  or  6  times. 

2.  Since  dirty  liquids  cause  discoloration  by  penetrating  the 
pores  of  the  brick  behind  the  glaze,  soak  the  brick  in  red  ink. 
The  stain  will  spread  through  the  clay  body  if  it  is  porous,  and 
show  through  the  enamel  if  the  latter  is  not  opaque. 

3.  Liability  to  hold  dirt  on  the  surface  is  tested  by  rubbing 
damp  soot  or  lamp  black  on  the  surface  of  the  glaze  and  then 
wiping  off.     If  the  glaze  is  not  smooth,  the  small  depressions 
will  hold  the  dirt. 


BUILDING  BRICKS  319 

4.  For  determining  the  resistance  of  the  glaze  to  corrosive 
vapor  the  following  is  suggested: 

A  piece  of  brick  is  placed  under  a  bell  glass,  exposed  to  the 
fumes  of  hydrochloric  acid  for  24  hours.  The  pieces  are  then 
removed  without  wiping  and  allowed  to  dry,  protected  from  the 
dust.  A  poor  brick  will  show  a  white  scum  on  its  glazed  surface, 
but  a  good  one  remains  unattacked. 

Glazes  on  fancy  tiles  and  art  wares  are  liable  to  fail  under  this 
treatment. 

5.  Resistance  to  percussion  is  sometimes  tested  with  an  impact 
machine,  the  brick  being  bedded  in  sand. 


CHAPTER  X. 
ARCHITECTURAL  TERRA   COTTA. 

Definition.  The  term  terra  cotta,  which  means  baked  earth, 
has  been  used  in  its  broadest  sense  to  include  both  pottery  and 
structural  objects  made  of  burned  clay  and  having  porous  body. 

Architectural  terra  cotta,  however,  is  a  narrower  term  and  is 
usually  applied  to  those  clay  products  employed  for  structural 
decorative  work  which  cannot  be  formed  by  machinery.  They 
are  consequently  molded  by  hand. 

Raw  Materials.  Architectural  terra  cotta  was  originally  made 
of  a  red-burning  clay,  but  at  the  present  day  this  practice  is  the 
exception,  and  most  of  this  type  of  ware  is  produced  from  a  mix- 
ture of  several  clays,  all  of  which  may  be  low-grade  fire  clays, 
and  therefore  of  buff-burning  color.  To  these  there  is  added 
some  grog  (ground  up  fire-brick  or  other  burned  clay),  in  order 
to  make  the  body  easier  to  dry  and  burn.  The  body,  after  burn- 
ing, is  generally  some  shade  of  buff,  but  this  is  not  a  matter  of 
great  importance  since  the  color  does  not  show  exteriorly,  for 
the  reason  that  an  opaque  skin  of  different  composition  from 
the  interior  hides  the  color  of  the  latter. 

Method  of  Manufacture.  The  manufacture  of  architectural 
terra  cotta  calls  for  considerable  skill  and  care,  and  the  demands 
of  the  architects  as  to  color  or  form  are  sometimes  quite  severe. 
Moreover,  the  ware  must  come  from  the  kiln  of  the  proper  dimen- 
sions to  fit  into  those  parts  of  the  building  for  which  it  is  de- 
signed, and  for  this  reason  the  maker  must  know  quite  accurately 
the  shrinkage  of  his  raw  materials. 

In  making  architectural  terra  cotta  the  clay  is  first  properly 
tempered  and  then  stored  in  cellar  bins  until  ready  for  use. 

Molding  is  done  in  plaster  molds,  into  which  the  clay  is  pressed 
by  hand,  unless  the  design  is  intricate  and  undercut,  in  which 
case  it  has  to  be  modeled. 

320 


g  H* 

I        - 


ARCHITECTURAL  TERRA  COTTA  323 

Small  and  simple  designs  can  be  formed  in  one  piece,  but 
larger  objects  have  to  be  constructed  of  several  separate  pieces, 
which  are  joined  together  when  set  in  the  building. 

After  molding,  the  ware  has  to  be  slowly  and  carefully  dried, 
subsequent  to  which  it  receives  its  surface  layer  of  slip. 

This  consists  of  a  mixture  of  clay,  quartz,  feldspar  and  other 
ingredients,  mixed  to  the  consistency  of  cream  and  sprayed  on 
to  the  air-dried  ware.  It  forms  a  dense  layer  in  burning.  The 
object  is  to  form  an  opaque  covering  on  the  surface  of  the  ware, 
which  not  only  serves  as  a  protective  skin  but  also  carries  the 
decorative  coloring. 

Terra  cotta  is  burned  in  special  kilns,  in  which  the  fire  gases 
do  not  come  in  contact  with  the  ware,  and  the  temperature  of 
burning  varies  at  different  works.  This  signifies  only  that  the 
clay  used  at  one  works  burns  hard  at  a  lower  temperature  than 
that  employed  at  another  factory. 

After  the  ware  comes  from  the  kiln,  the  different  parts  of  a 
given  design  are  matched  together,  to  see  if  they  fit  properly. 

Terra  cotta  is  now  made  in  a  large  number  of  shades  and 
colors. 

The  surface  slip  may  be  of  dull  finish,  or  glazed,  either  matt 
(dull)  or  bright.  The  dull  finish  is  often  decorated  so  as  to 
match  or  imitate  different  types  of  building  stone  in  color  and 
pattern.  Glazed  terra  cotta  may  show  either  one  color  or 
a  number  of  colors  (polychrome)  arranged  to  form  a  design. 

The  tendency  in  modern  terra-cotta  manufacture  is  to  make 
smaller  pieces  than  formerly.  There  is  also  a  reduction  in 
size  of  cornice  blocks,  which  can  be  easily  anchored  to  the 
building.  Brackets  are  usually  the  largest  pieces,  with  the 
exception  of  exterior  and  interior  mitre  pieces,  which  have  to 
be  made  in  one  piece. 

It  is  comparatively  easy  to  make  columns  6  feet  long  and 
keep  them  straight  in  burning,  but  they  are  usually  cut  up 
into  sections.  A  fluted  column  requires  greater  care  than  a 
smooth  one.  Precautions  have  to  be  taken  to  prevent  long 
columns  from  warping  in  the  kiln  and  drums  from  spreading 
out  on  the  end  upon  which  they  rest  in  drying  and  burning. 


324  BUILDING  STONES  AND   CLAY-PRODUCTS 

Full  columns  are  rarely  made  in  one  piece,  but  are  cut  up  in 
segments  and  joined  together. 

Ordinary  terra-cotta  pieces  are  usually  from  12  to  18  inches  in 
length,  and  vary  in  thickness  according  to  the  wall. 

Some  excellent  and  skilful  modelling  of  figures,  capitals,  floral 
designs,  etc.,  is  often  done. 

Polychrome  terra  cotta,  or  architectural  fayence,  of  high 
artistic  merit  is  now  made  by  several  art  potteries  and  terra- 
cotta works.  It  is  rapidly  finding  wide  favor  and  is  extensively 
used  for  both  interior  and  exterior  decoration. 

Properties  of  Terra  Cotta.  Since  terra  cotta  is  often  used  as  a 
substitute  for  stone,  its  properties  as  compared  with  the  latter 
may  be  mentioned. 

The  advantages  claimed  are:  Less  weight  per  cubic  foot; 
greater  durability;  greater  range  of  colors;  finer  lines  of  orna- 
mentation; better  fire  resistance;  cheaper  cost. 

The  disadvantages  claimed  are  inability  of  many  pieces  to 
stand  hard  knocks;  unadapted  to  massive  work;  more  costly 
to  lay. 

Terra  cotta  for  architectural  work  should  be  hard  burned  but 
not  vitrified;  the  different  pieces  should  fit  together  well;  the 
absorption  of  the  body  should  be  moderately  low;  it  should  not 
become  discolored  by  soluble  salts;  the  surface  should  be  steel 
hard. 

If  the  ware  is  covered  with  a  glaze  the  latter  should  be  free 
from  cracks,  crazes,  pimples  or  holes. 

In  the  writer's  opinion  architects  should  exercise  more  caution 
in  the  acceptance  of  glazed  terra  cotta,  as  not  a  few  very  poor 
jobs  are  to  be  seen  in  both  the  United  States  and  Canada. 

Testing  Terra  Cotta.  There  are  few  published  tests  of 
terra  cotta,  nor  have  any  standard  series  of  tests  been 
recommended. 

The  ware  can  be  tested  for  absorption  and  soluble  salts. 
Crushing  tests  can  also  be  made.  A  number  of  the  latter  type 
have  been  made  by  R.  F.  Grady1  of  St.  Louis,  and  some  of  these 
are  given  below. 

1  American  Ceramic  Society,  Transactions,  X,  p.  135;   XI,  p.  75;   XII,  p.  90. 


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ARCHITECTURAL   TERRA  COTTA 


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328 


BUILDING  STONES  AND   CLAY-PRODUCTS 


Further  tests  made  by  Grady,1  to  determine  the  relation  be- 
tween absorption  and  crushing  strength  of  a  terra-cotta  body, 
did  not  show  uniform  results;  for  while  the  absorption  de- 
creased with  harder  burning,  the  crushing  strength  did  not  show 
a  steady  increase. 

The  figures  are  given  below,  but  the  one  series  of  tests  cannot, 
of  course,  be  considered  as  absolutely  conclusive.  The  pieces 
tested  were  two-inch  cubes.  The  temperatures  below  are  ex- 
pressed in  Seger  Cones,  with  the  theoretic  melting  point  placed 
after  each. 


Cone. 

Theoretic 
melting  point. 

Absorption  , 
per  cent. 

Crushing  strength, 
Ibs.  per  sq.  in.   - 

Deg.  C. 

04 

1070 

10.85 

3319 

O2 

IIIO 

10.73 

3248 

I 

1150 

io.  16 

3354 

2 

1170 

9.76 

3585 

3 

1190 

9-55 

4007 

4 

1210 

9.60 

3499 

5 

1230 

.    9.36 

3320 

6 

1250 

8-37 

3867 

6+ 

7.91 

4132 

In  a  test  made  by  the  New  York  Architectural  Terra  Cotta 
Company,  a  terra-cotta  modillion,  io  inches  high  and  with 
8  inches  face,  was  loaded  with  4083  pounds  of  pig  iron  without 
breaking. 

Terra-cotta  Scum.  Terra-cotta  makers  are  often  troubled 
with  a  yellowish  or  greenish  yellow  scum  that  appears  on  the 
surface  of  terra  cotta,  sometimes  not  until  after  placement  in 
the  building.  Cases  <  in  which  an  entire  order  has  been  rejected 
because  of  this  trouble  have  come  to  the  author's  notice. 

The  scum  appears  to  be  caused  by  soluble  compounds  of  the 
rare  element  vanadium,  and  most  terra-cotta  makers  have 
trouble  in  coping  with  the  difficulty. 

Fire-resisting  Properties.  Freitag  states  that  "  The  be- 
havior of  architectural  terra  cotta  under  fire  test  in  the  Balti- 
more and  San  Francisco  fires  was  very  disappointing.  Numerous 


American  Ceramic  Society,  Transactions,  XII,  p.  90. 


ARCHITECTURAL  TERRA  COTTA  331 

accounts,  of  the  former  fire  especially,  have  dwelt  upon  the 
apparently  excellent  showing  made  by  this  material.  From 
the  street,  or  from  a  superficial  examination  only,  many  brick 
and  terra-cotta  walls  appeared  to  be  little  injured,  when,  in 
fact,  the  terra  cotta,  although  retaining  its  form,  was  quite 
destroyed.  Thus,  in  several  buildings  where  walls  of  this  char- 
acter seemed  to  have  sustained  but  trifling  injury,  the  adjusted 
fire  loss  and  actual  reconstruction  told  a  far  different  story. 
Brick  walls  with  terra-cotta  trim  were  entirely  replaced  in  the 
Union  Trust  Company's  and  Herald  Buildings,  while  in  the 
Calvert  Building  the  adjusted  loss  on  ornamental  terra  cotta 
was  73.5  per  cent,  in  the  Equitable  Building  70  per  cent  and 
in  the  Maryland  Trust  Company's  Building  75  per  cent. 

"The  report  of  the  National  Fire  Protection  Association  states 
that  '  Good  terra-cotta  wall  trim,  when  reasonably  plain  and 
free  from  ornamentation  involving  irregular  shapes,  is  superior 
to  stone  but  not  so  desirable  as  brick.'  This  carefully  guarded 
statement  on  the  part  of  the  underwriters  who  framed  that 
report  was  further  justified  by  the  showing  made  by  archi- 
tectural terra  cotta  in  the  San  Francisco  conflagration. 

"  This  says: 1  '  Of  the  terra-cotta  fronts,  most  were  destroyed, 
for  instance  the  Bullock  and  Jones  Building.  Terra-cotta  brick 
spalled  everywhere.  .  .  .  Either  stone,  brick  or  terra  cotta 
was  used  around  windows,  and  here  the  damage  was  worst. 
Many  fronts,  apparently  in  good  order,  must  be  removed.  In 
the  Mills  Building  there  was  hardly  a  window  opening  in  which 
the  terra  cotta  sills,  jambs  and  heads  were  not  badly  cracked. 
From  the  street  they  had  the  appearance  of  being  in  good 
order.'  " 

Freitag  believes  that  the  injury  by  fire  to  architectural  terra 
cotta  is  due  to:  "(a)  direct  flame  action,  (b)  shattering  due  to 
more  or  less  sudden  changes  in  temperature,  or  (c)  mechanical 
damage  caused  by  poor  construction  or  by  the  expansion  of 
covered  steel  members." 

"  Slight  damage  usually  results  from  the  first  and  second 
causes,  except  where  the  material  is  highly  ornamented,  or 

1  Quoted  by  Freitag  from  Trans.  Am.  Soc.  Civ.  Engrs.,  LIX,  p.  238. 


332  BUILDING  STONES  AND   CLAY-PRODUCTS 

where  manufactured  with  too  thin  surfaces  or  dividing  webs. 
To  be  efficient  under  fire  test,  architectural  terra  cotta  should  be 
of  as  plain  a  surface  and  design  as  possible,  and  with  no  thick- 
ness of  material  less  than  one  and  one-half  inches." 

The  largest  part  of  the  damage  to  architectural  terra  cotta  is 
said  to  be  due  to  the  third  cause. 


CHAPTER  XI. 

HOLLOWWARE   FOR  STRUCTURAL  WORK  AND   FIRE- 
PROOFING. 

UNDER  this  heading  are  included  a  number  of  hollow  shapes, 
of  varying  size,  form  and  porosity,  but  all  having  usually  one  or 
more  cross  webs  for  strengthening  purposes. 

Types  of  Hollowware.  The  following  terms  are  applied  to 
the  different  types: 

Fireproofing.  This  is  a  general  name  applied  to  those  forms 
used  in  the  construction  of  floor  arches,  partitions  and  furring  for 
walls,  columns,  girders  and  for  other  purposes  in  fireproof  build- 
ings. Terra-cotta  lumber  is  also  a  general  term  applied  to  those 
forms  of  fireproofing  which  are  comparatively  soft  and  porous, 
owing  to  the  addition  of  a  large  percentage  of  sawdust  to  the 
clay.  The  former  burns  off  in  the  kiln,  thus  leaving  the  product 
so  soft  and  porous  that  nails  can  be  driven  into  it.  Hollow 
blocks  are  forms  which  are  used  for  both  exterior  and  interior 
walls,  in  either  fireproof  or  nonfireproof  buildings.  Hollow 
brick  are  like  hollow  blocks  in  form,  but  no  larger  than  many 
ordinary  building  brick,  and  are  much  used  for  partitions  on 
account  of  their  light  weight  and  non-conductivity  for  sound 
and  heat.  Book  tiles  are  flat,  hollow  tiles,  which  have  two  seg- 
mental  edges.  They  resemble  a  book  in  section.  Furring 
blocks  is  a  name  applied  to  slabs  which  are  placed  against  ex- 
terior walls  to  secure  insulation  against  dampness,  heat,  cold 
and  sound. 

Raw  Materials  and  Manufacture.  Hollowware  is  made  from 
either  red  or  buff-burning  clays  or  shales,  or  a  mixture  of  these 
with  fire  clay,  usually  of  low  grade.  The  material  is  molded  in 
a  stiff-mud  machine,  dried  by  artificial  heat  in  tunnels  and 
burned  in  some  form  of  permanent  kiln,  usually  at  a  moderate 
temperature,  and  not  as  a  rule  to  the  vitrifying  point. 

333 


334  BUILDING  STONES  AND   CLAY-PRODUCTS 

Defects  which  the  ware  may  show  are  cracks,  formed  in  drying 
and  burning,  and  blisters  or  pimples,  the  latter  caused  by  lumps 
of  clay,  pyrite,  or  siderite.  The  color,  as  already  stated,  is 
usually  red,  but  unless  the  product  is  a  hollow  block  for  front 
walls  the  color  is  not  a  matter  of  great  importance.  The  absorp- 
tion varies  with  the  hardness  of  burning,  and  quantity  of  ground 
brick,  sand,  or  sawdust  added. 

Fireproofing.  The  object  of  fireproofing  is  not  only  to  protect 
the  inclosed  metal  parts  of  the  building  from  the  direct  action 
of  the  flames  in  case  of  fire,  but  the  hollow  spaces  also  serve  as 
nonconductors  of  heat.  The  material  should  not  be  vitrified. 
It  is  sometimes  made  from  shale  or  common  clay,  or  a  mixture 
of  these  with  low-grade  fire  clay. 

There  exists  a  diversity  of  opinion  regarding  the  relative 
merits  of  porous  and  hard-burned  fireproofing,  especially  when 
used  for  floor  arches  set  in  between  the  I-beams. 

Porous  fireproofing,  it  is  argued,  is  easily  cut  and  nails  or 
screws  can  be  driven  into  it.  It  is  also  thought  to  show  a  better 
resistance  to  suddenly  applied  loads. 

Hard-burned  fireproofing  is  not  readily  cut,  but  must  be 
broken.  It  is  more  brittle  than  the  porous  and  therefore  more 
liable  to  fail  under  shocks. 

An  intermediate  type,  known  as  semi-porous  is  regarded  by 
many  as  the  best. 

Under  static  loads  the  hard-burned  fireproofing  is  said  to  be 
stronger  than  the  porous,  where  equal  sectional  areas  are  com- 
pared, but  this  deficiency  on  the  part  of  the  porous  can  be  made 
up  by  increasing  the  thickness  of  the  webs. 

In  making  an  arch  for  flooring,  three  shapes  of  blocks  are 
necessary,  viz:  the  skewback,  key,  and  lengtheners,  fillers  or 
intermediates. 

The  blocks  used  for  floor  arches  may  be  of  two  types  of  con- 
struction, viz.,  end  or  side. 

In  the  end-construction  arches  the  blocks  are  set  end  to  end, 
so  that  the  cells  run  at  right  angles  to  the  beams,  or  from  beam 
web  to  beam  web. 

The  arch  pressure  is  therefore  against  the  ends  of  the  blocks, 


HOLLO WWARE  FOR  STRUCTURAL  WORK  AND  FIREPROOFING     337 

and  since  hollow  tiles  show  greater  strength  under  end  compres- 
sion than  side  compression,  an  end-construction  arch  will  de- 
velop about  50  per  cent  more  strength,  for  the  same  weight, 
than  a  side-construction  one.  This,  of  course,  is  on  the  assump- 
tion that  the  arch  is  properly  set. 

In  the  side-construction  arch,  the  lengtheners  and  key  are 
set  side  by  side,  and  the  openings  run  parallel  with  the  girders  on 
which  the  base  of  the  arch  rests. 

Side-construction  skewbacks  may  be:  (i)  plain,  or  without 
any  provision  for  protecting  the  beam  flange;  (2)  lipped,  or 
with  a  protecting  lip  attached  (Plate  LV);  (3)  soffited,  that  is, 
with  a  bevel  at  the  bottom  of  the  skewback  to  hold  the  soffit 
tile  in  place  under  the  beam. 

Lipped  skews  are  less  used  than  formerly,  as  the  lip  may  be 
warped  during  drying  and  burning,  or  be  broken  during  erection. 

End-construction  lengtheners  are  now  more  widely  used  than 
side-construction  ones. 

A  lengthener  in  end  construction  is  usually  12  inches  wide 
and  12  inches  long,  while  the  interior  webs  vary  with  the  depth 
and  required  strength.  Six-inch  blocks  can  be  made  without 
interior  horizontal  webs. 

"  For  semi-porous  blocks 1  the  usual  thickness  of  the  outer 
shells  is  f  inch,  and  for  the  interior  webs  about  i  inch.  The 
cells  should  preferably  be  not  over  3^  inches  in  either  direction. 

"Both  end-  and  side-construction  keys  are  used  in  end-con- 
struction arches,  the  former  being  generally  used  when  the 
span  requires  a  key  over  6  inches  wide,  and  the  latter  for  6 
inches  or  less. 

"The  objections  to  end-construction  arches  are,  —  first,  that 
the  blocks  cannot  be  made  to  break  joint,  —  second,  that  a 
true  end-bearing  and  mortar  joint  is  more  difficult  to  obtain 
than  with  side-construction  blocks,  —  and  third,  that  more  mor- 
tar must  be  used  on  account  of  the  waste  in  the  cells.  Objec- 
tions one  and  two  can  be  disregarded  in  view  of  the  excess 
strength  obtained  through  using  the  end-construction  method, 
while  objection  three  is  of  small  consequence." 
1  Freitag,  /.  c.,  p.  557. 


338 


BUILDING  STONES  AND   CLAY-PRODUCTS 


The  various  depths  of  arch  blocks,  weights  per  square  foot  of 
arches,  and  permissible  spans  for  standard  side-construction 
arches  are  as  follows: 1 


Spans  allowable  between  I-beams. 

Depth  of  arch, 
inches. 

Weight,  pounds  per 
square  foot. 

Arch  set  flat,  feet  and 
inches. 

Set  with  slight  camber, 
feet  and  inches. 

6 

24-26 

4-0 

4-6 

7 

26-28 

4-6 

5-6 

8 

27-32 

5-0 

6-0 

9 

29-36 

5-6 

7-0 

10 

33-38 

6-6 

7-6 

12 

37-44 

7-o 

8-6 

NOTE.  —  The  heavier  weights  are  the  ones  commonly  used. 

The  weights  of  standard  end-construction  arches  and  per- 
missible span  are  given  as  below. 


Spans  allowable  between  I-beams. 

inches. 

square  foot. 

Arch  set  flat,  feet  and 
inches. 

Set  with  slight  camber, 
feet  and  inches. 

6 

2O-26 

4-6 

5-o 

7 

22-29 

5-o 

5-9 

8 

24-32 

5-6 

6-6 

9 

26-36 

6-0 

7-0 

10 

28-38 

6-6 

7-6 

12 

30-44 

7-6 

9-0 

15 

37-50 

9-0 

1  0-0 

Furring  Blocks.  These  are  much  used  in  refrigerator  or  cold- 
storage  buildings,  and  other  places  where  it  is  necessary  to  pre- 
serve a  uniform  temperature. 

In  small  structures,  as  stores  and  dwellings,  a  single-thickness 
block,  with  a  i-inch  or  2-inch  air  space  may  be  used. 

Blocks  12  by  1 6  by  2  inches  weigh  8  pounds  per  square  foot. 
Double-thickness  furring  blocks  are  made  from  3  to  6  inches 
thick. 

Hollow  Block  and  Brick.  The  use  of  hollow  block  as  a  sub- 
stitute for  stone  or  brick  for  ordinary  work  of  construction  of 

1  Freitag,  /.  c.,  p.  554. 


HOLLOWWARE  FOR  STRUCTURAL  WORK  AND  FIREPROOFING     339 

houses  as  well  as  large  buildings  is  increasing  rapidly,  especially 
in  the  central  states. 

Hollow  blocks  employed  for  exterior  walls  are  often  vitrified 
or  nearly  so,  and  the  advantages  claimed  for  them  over  common 
brick  are:  (i)  Lighter  weight  per  cubic  foot  of  wall;  (2)  Suffi- 
cient strength  to  insure  a  large  safety  factor;  (3)  Much  less  clay 
required;  (4)  Lower  transportation  costs  for  a  given  bulk  be- 
cause of  less  weight;  (5)  Full  protection  against  dampness  and 
temperature;  (6)  Less  labor  required  to  lay  in  wall. 

The  surface  is  usually  smooth,  or  ribbed  to  hold  the  mortar, 
but  for  ornamental  purposes  the  block  can  be  made  with  one 
decorated  surface. 

A  number  of  different  shapes  and  sizes  of  hollow  blocks  are 
made,  and  while  the  majority  of  them  agree  in  being  12  inches 
long,  the  other  two  dimensions  may  vary.  Thus,  of  the  blocks 
which  are  12  inches  long,  the  other  dimensions  may  be  6  by  3 
inches,  6  by  4  inches,  6  by  5  inches,  6  by  6  inches,  6  by  7  inches, 
etc.,  or  perhaps  3  by  8  inches,  or  3  by  12  inches,  etc. 

A  block  4  by  8  by  1 6  inches  usually  weighs  20  pounds;  one 
8  by  8  by  1 6  inches,  34  pounds;  and  a  cubic  foot  of  hollow  block 
averages  40  pounds. 

Hollow  blocks  when  used  for  partitions  are  not  necessarily  of 
vitrified  character.  Hollow  brick  employed  for  partitions  are 
commonly  more  or  less  porous.  They  are  commonly  made  of 
a  red-burning  clay,  but  even  cream-burning  calcareous  clays 
have  been  employed  for  this  purpose. 

In  recent  years  a  mixture  of  clay  and  diatomaceous  earth 1  has 
been  made  into  partition  bricks  in  Virginia  and  California. 

Freitag2  gives  the  following  as  essential  requirements  for  a 
fireproof  partition:  (i)  Architectural  service;  (2)  Fire- resisting 
service;  (3)  Heat-retarding  qualities;  (4)  Stability  against  shock, 
water  streams,  etc.;  (5)  Deadening  qualities  to  prevent  trans- 
mission of  sound. 

The  square  blocks  for  partitions  are  commonly  12  by  12 
inches  for  the  body  of  the  wall,  and  6  by  12  inches,  and  8  by  12 
inches  for  the  end  spaces  or  tops  of  the  partitions, 

1  Usually,  though  incorrectly,  called  infusorial  earth.         *  Loc.  cit,  p.  236. 


340 


BUILDING  STONES  AND   CLAY-PRODUCTS 


For  brick-shaped  blocks,  the  sizes  made  in  semi-porous  terra 
cotta  are  6  by  8  by  12  inches,  6  by  12  by  12  inches,  4  by  12  by 
12  inches,  4  by  8  by  12  inches,  3  by  12  by  12  inches,  and  2  by 
8  by  1 2  inches.  Porous  partition  blocks  may  run  4  by  8  by  1 2 
inches,  4  by  12  by  12  inches,  6  by  8  by  12  inches,  6  by  12  by  12 
inches,  2  by  12  by  12  inches,  and  2  by  8  by  12  inches. 

Frei  tag  Ogives  the  weights  per  square  foot  of  tile  partitions, 
without  plaster,  as  being  on  the  average  about  as  follows: 


2-in. 

3-in. 

4-in. 

5-in. 

6-in. 

Semi-porous  tile  

Lbs. 

12 

Lbs. 
1C 

Lbs. 
16 

Lbs. 
18 

Lbs. 

24 

Porous  tile  

14- 

17 

18 

2O 

26 

If  plastered  on  both  sides,  add  10  pounds  per  square  foot  to 
the  above. 

Tests  of  Hollow  Blocks.  A  number  of  scattered  tests  of  this 
class  of  ware  have  been  published. 

The  following  tests  of  hollow  blocks  are  given  by  the  Iowa 
Geological  Survey:2 

BLOCKS  EMBEDDED   IN   PLASTER  TOP  AND   BOTTOM. 


No. 

Approximate  dimen- 
sions. 

Position. 

Crushing  strength,11 
tons  per  square  foot. 

I 

4X8X12 
4X8X12 
4X8X12 

Flatwise 
Endwise 
Edgewise 

78.1  + 
230.8 
I7I-5  + 

2 

4X8X12 
4X8X12 
5X5X12 
4X4X12 

Flatwise 
Edgewise 
Flatwise 
Flatwise 

64.0 
59  -6 
39-i 
56.5 

3 

5X8X12 
5X8X12 

Flatwise 
Edgewise 

30.2 
65.0 

4 

5X8X12 
5X8X12 
5X8X12 

Flatwise 
Endwise 
Edgewise 

47.0 
131.0 
59-9 

5 

5X8X16 
5X8X16 
8X8X16 

Flatwise 
Flatwise 
Flatwise 

49.0 

55-5  + 
58.0 

c.,  p.  399- 


2  Iowa  Geol.  Surv.,  XIV,  p.  600,  1904. 


HOLLOWWARE  FOR  STRUCTURAL  WORK  AND  FIREPROOFING     341 

Architects  usually  allow  from  five  to  ten  tons  per  square  foot 
pressure  on  brick  masonry.  Even  with  this  the  hollow  brick 
show  a  large  safety  factor. 

In  another  test1  it  was  found  that  blocks  8  by  8  by  16  inches 
developed  an  ultimate  strength  of  2500  pounds  per  square  inch, 
in  center  web  blocks,  and  1969  pounds  per  square  inch  on  gross 
area;  and  6000  pounds  per  square  inch  on  net  area  in  corner 
blocks. 

In  the  Report  on  Tests  of  Metals,  etc.,  for  1895,  published  by 
the  War  Department,  there  are  given  a  number  of  tests  of  fire- 
proofing,  from  which  the  following  tests  are  extracted. 

1  Brickbuilder,  Vol.  XV,  p.  164,  1908;  British  Clayworker  Suppl.,  XV,  p.  LIT, 
1906. 


342 


BUILDING   STONES   AND    CLAY-PRODUCTS 


^ 


§: 


I  H 


M 
3 


* 

O 


i      I 


HOLLOW  WARE  FOR  STRUCTURAL  WORK  AND  FIREPROOFING     343 


sils 


13          ro 


i  1 

3  {^ 

a   v 


s 

S.        2 


ri 


344 


BUILDING  STONES  AND  CLAY-PRODUCTS 


111 


HOLLOWWARE  FOR  STRUCTURAL  WORK  AND  FIREPROOFING     345 

From  a  series  of  tests  of  crushing  strength  and  absorption 
made  by  V.  G.  Marini,1  the  latter  has  suggested  some  tentative 
specifications  for  hollow  clay  tile  building  blocks. 

Some  of  the  tile  were  built  up  in  columns  of  different  dimen- 
sions, and  with  the  tile  laid  in  different  positions  in  the  various 
columns,  these  being  then  tested  for  their  crushing  strength. 
Other  tile  were  tested  singly. 

From  the  results  of  these  tests  it  was  noticed  that  in  the  case 
of  those  tile  having  an  absorption  of  less  than  12  per  cent,  and 
with  the  vertical  webs  spaced  not  more  than  4  inches  apart, 
centre  to  centre,  and  with  a  web  thickness  of  at  least  20  per  cent 
of  the  height,  the  blocks  being  placed  so  that  the  vertical  webs 
were  directly  over  each  other,  no  single  tile  or  column  failed 
under  a  less  load  than  3465  pounds  per  square  inch  of  the  vertical 
web  section. 

The  following  specifications  are  suggested  for  hollow  clay 
tile,  the  tile  to  be  laid  with  the  voids  horizontal. 

(1)  Character  of  Body.    Tile  to  be  made  of  shale  or  fire  clay, 
or  any  clay  that  will  burn  to  a  good  dense  body  without  undue 
warping  or  checking,  and  must  be  burned  to  such  a  degree  of 
hardness  that  they  will  not  absorb  more   than   12   per  cent 
moisture. 

(2)  Webs.    Vertical  webs  should  be  spaced  not  more  than 
4  inches  apart,  centre  to  centre,  and  should  have  a  thickness  of 
at  least  20  per  cent  of  their  height. 

(3)  Bedding.     To  secure  thorough  bedding,  tile  should  be  so 
constructed  as  to  preclude  mortar  beds  of  more  than  4^  inches 
(same  as  brickwork)  in  width,  and  should  be  laid  with  broken 
joints  and  be  thoroughly  bedded  and  bonded. 

(4)  Quality.     Tile   should  be   true   and   free   from  injurious 
checks  and  cracks. 

(5)  Position  in  Wall.    Tile  should  be  so  laid  in  wall  that 
the  vertical  webs  are  in  vertical  alignment  with  the  vertical  webs 
of  the  adjacent  tiles  below. 

(6)  Loads.    Tile  walls  should  be  loaded  with  not  more  than 
200  pounds  per  square  inch  of  vertical  web  section. 

1  The  Engineering  News,  Vol.  67,  p.  248. 


346  BUILDING  STONES  AND  CLAY-PRODUCTS 

(7)  Thickness  oj  Walls.     Permissible  thickness  of  load  same 
as  for  common  brick. 

(8)  Joist  or  Bearing.     Where  joists  or  beams  are  set  in  walls, 
they  should  have  a  bearing  extending  over  at  least  two  of  the 
vertical  webs. 

Fire  Tests.  Since  certain  forms  of  hollow  blocks  are  used  for 
combined  fireproofing  and  structural  purposes,  a  properly  made 
fire  test  is  of  value. 

In  the  test  of  fireproof  floor  construction  recommended  by  the 
American  Society  for  Testing  Materials,  a  standard  test  structure 
is  used,  with  the  hollow  blocks  built  into  a  floor.  A  working 
load  of  150  pounds  per  square  inch  is  distributed  over  the  floor, 
without  arching  effect,  and  is  carried  by  the  floor  during  the 
test. 

The  test  must  be  made  within  forty  days  after  construction, 
and  artificial  drying  is  allowed. 

The  test  itself  will  consist  in  subjecting  the  floor  to  the  con- 
tinuous heat  of  a  wood  fire  averaging  not  less  than  1700°  F. 
for  4  hours.  The  temperature  shall  be  measured  by  means  of  a 
standard  pyrometer  at  two  points  at  least,  and  readings  taken 
every  two  minutes.  At  the  end  of  the  heat  test  the  floor  is  cooled 
by  a  stream  of  water  thrown  on  its  under  surface.  A  load  of  600 
pounds  per  square  inch  is  then  distributed  over  the  floor.  The 
test  shall  not  be  regarded  as  successful  unless  the  following  con- 
ditions are  noticed :  No  fire  or  smoke  shall  pass  the  floor  during 
the  fire  test;  the  floor  must  safely  sustain  the  loads  prescribed ; 
the  permanent  deflection  must  not  exceed  J  inch  for  each  foot 
of  span  in  either  slab  or  beam. 

In  a  test  made  by  Professor  I.  H.  Woolson,1  a  large  chamber 
with  brick  walls  was  used,  and  this  was  floored  over  on  top  with 
an  arch  of  six-inch  hollow  tile  covered  by  four  inches  of 
cement. 

This  was  loaded  to  270  pounds  pressure  per  square  inch  and 
fire  built  underneath,  burning  four  hours  with  an  average  tem- 
perature of  1700°  F.  While  still  red  hot  a  stream  of  water  was 
played  on  under  side  of  floor  for  ten  minutes  at  a  pressure  of 

1  Brickbuilder,  XIV,  p.  33,  1905. 


HOLLOWWARE  FOR  STRUCTURAL  WORK  AND  FIREPROOFING      347 

from  75  to  80  pounds.  The  cement  spalled  off,  but  the  tile 
showed  no  cracking,  and  the  maximum  deflection  determined 
by  careful  measurements  was  0.4  inch  sinking  of  floor. 

Freitag  1  believes  that  the  behavior  of  fireproofing  in  a  fire 
is  due  not  alone  to  the  character  of  the  material  itself,  but  that 
contributing  factors  are  the  conditions  of  the  test,  details  of 
construction,  etc. 

He  concludes  that  "  porous  or  even  semi-porous  tile  can,  and 
generally  does,  withstand  any  reasonable  fire  and  water  test, 
provided  that  the  material  is  of  sufficient  thickness  and  is  used 
in  an  intelligent  manner." 

In  comparing  hard-burned  and  porous  terra  cotta,  Freitag 
further  says: 

"  Hard-burned  terra  cotta  as  a  heat  insulator  depends  for 
value  entirely  upon  its  cellular  structure,  protection  being 
afforded  only  by  the  non-heat-conducting  air  spaces.  The  ma- 
terial itself  conducts  heat  much  more  readily  than  the  porous 
kind.  To  be  efficient,  therefore,  the  air  spaces  in  hard-burned 
tile  must  be  of  adequate  size  and  number  to  insulate  the  mate- 
rial to  be  protected.  When  cooled  by  water,  sudden  contrac- 
tion is  liable  to  occur,  thereby  cracking  the  blocks.  If  made  of 
a  good  refractory  clay,  blocks  with  two  or  more  air  spaces  are 
very  liable  to  have  the  outer  webs  destroyed  under  this  action, 
as  was  well  illustrated  by  the  hard-tile  floor  arches  in  the  first 
Home  Store  Building  of  Chicago.  This  was  due  to  the  ina- 
bility of  the  material  to  withstand  the  inequalities  of  expansion 
and  contraction  caused  by  the  heating  of  one  side  of  the  arches 
only.  The  blocks  usually  break  first  in  the  corners,  because 
the  strain  is  greatest  there,  and  the  tile  weakest.  The  strain  is 
greatest  in  the  corners  because  the  expansion  of  the  one  side 
tends  to  shear  it  from  the  adjoining  sides,  and  it  is  weakest  in 
the  corners  because  if  there  is  any  initial  stress  in  the  mate- 
rial, it  would  more  naturally  occur  there  than  elsewhere. 

"Even  if  not  cooled  with  water,  other  fires  have  shown  that 
hard-burned  terra  cotta  will  crack  and  fall  to  pieces  under 
severe  heat  alone. 

1  "  Fire  Prevention  and  Fire  Protection,"  p.  236. 


348  BUILDING  STONES  AND   CLAY-PRODUCTS 

"Porous  terra  cotta  is  non-heat-conducting  itself,  without  ref- 
erence to  its  form.  It  is  made  in  solid  as  well  as  in  hollow 
forms.  The  best  products  of  a  porous  nature  have  resisted 
fire  and  water  far  better  than  the  best  hard  tile.  For  column 
and  girder  protections,  where  the  blocks  do  not  carry  loads,  the 
porous  material  is  very  generally  used,  but  in  floor  construction 
many  architects  prefer  to  use  the  hard-burned  variety  on  account 
of  its  greater  strength  and  cheaper  price. 

" Semi- porous  terra  cotta  is  largely  used.  It  is  stronger  than 
porous  tile  and  less  liable  to  crack  than  hard  tile." 


CHAPTER  XII. 
ROOFING  TILE.1 

ALTHOUGH  widely  used  for  many  years  abroad,  the  employ- 
ment of  roofing  tile  in  the  United  States  has  not  been  so  exten- 
sive. The  industry,  however,  has  shown  a  very  healthy  growth. 

The  standard  roofing  tile  which  are  for  exterior  covering  and 
decoration  are  made  in  the  following  shapes:  (i)  Shingle;  (2) 
Mission,  Mexican  or  Roman,  called  also  Old  Spanish  and  Normal; 
(3)  Spanish  or  S  tile;  (4)  Interlocking. 

Shingle  Tile.  These  are  perfectly  flat,  and  laid  on  the  roof  in 
the  same  manner  as  slate.  They  are  regarded  by  many  as  plain 
and  monotonous,  although  an  attempt  has  been  made  to  over- 
come this  by  making  them  with  strong  vertical  ridges  and  valleys. 


Gothic.          Round  Round      New-York  Washington     Square  Phila. 

Corner.  End.  Cut.  Cut.  End.  Cut. 

Fig.  14.  — Different  styles  of  shingle  tile. 

A  shingle  tile  which  is  flat  will,  when  properly  laid,  make  a 
water-tight  roof,  but  the  main  objection  to  it  is  the  weight, 
which  is  200  to  400  pounds  more  per  square  than  the  Spanish 
or  interlocking.  It  takes  about  400  tile  to  cover  a  square,  and 
the  time  required  for  laying  shingle  tile  is  longer  than  in  the 
case  of  other  types. 

One  shingle  tile  made  at  Huntington,  W.  Va.,  measures  6  by 
I3^  by  J  inches,  weighs  noo  pounds  per  square,  436  tile 
being  required,  laid  with  5^  inches  to  the  weather. 

1  An  excellent  report  on  the  properties  and  manufacture  of  roofing  tile  has  been 
issued  by  the  Ohio  Geol.  Surv.,  4th  Ser.,  Bull.  n. 

349 


350 


BUILDING   STONES  AND   CLAY-PRODUCTS 


Those  made  at  Parkersburg,  W.  Va.,  weigh  about  1200  pounds 
per  square  for  a  7  by  i4|-inch  tile,  laid  350  tile  per  square, 
with  6  inches  to  the  weather. 

Shingle  tile  may  have  either  square  or  rounded  edges,  the 

latter  being  more  artistic  and  easier  to  make.     It  is  also  claimed 

that  vertical  lines  are  accentuated  more  with  round-edged  tile. 

Old   Spanish,   Normal,   Mexican,   Mission  or  Roman  Tile. 

These  names  are  all  applied  to  a  roofing  tile  of  semicircular 

cross  section,  slightly  smaller  at  one 
end  than  the  other,  so  that  they  can 
be  laid  overlapping.  They  are  laid 
with  the  concave  and  convex  sides 
up  alternately,  so  that  one  straddles 
two  others. 

Sometimes  a  tile  of  this  style  is 
laid  in  connection  with  a  pan  tile; 
that  is,  a  flat  tile  with  upturned 
edges. 

Ffe.  15-  -Old  Spanish  or  Mission         The  use  of  these  Qld  Spanish  tile 
Tile.     (Akron  Roofing  Tile  Com-     .  ^  .  ^    ,  .     f.      TT    ^    , 

^  is  somewhat  restricted  in  the  United 

States,  but  they  have  been  much 

used  in  the  southwest  to  accompany  the  mission  style  of 
architecture. 

The  Old  Spanish  tile  roof  is  not  water-tight,  it  has  to  be  laid 
in  elastic  cement. 

The  ordinary  size  is  6  by  13  by  f  inches,  and  the  weight  of 
tiles  f  inch  thick  is  noo  pounds  per  square;  \  inch  thick,  1200 
pounds. 

Modern  Spanish  or  S  Tiles.  These  have  been  made  to  over- 
come technical  defects  of  preceding.  Their  section  in  one  case 
represents  a  letter  S,  or  in  the  other  a  combination  of  Old  Spanish 
and  pan  tile  made  in  one  piece.  The  objection  to  these  tile 
is  that,  like  the  preceding,  they  must  be  laid  in  cement. 

However,  in  spite  of  these  objections,  they  are  likely  to  be 
widely  used,  because  they  can  be  made  cheaper  than  an  inter- 
locking Spanish  tile  and  are  as  good  from  an  architectural 
standpoint. 


ROOFING  TILE  351 

Interlocking  Spanish  tile  are  made  with  side  and  end  locks, 
or  tongues  and  grooves  on  the  upper  surface  of  the  tile  which 
intermesh  with  corresponding  grooves  and  tongues  on  the  lower 
surface  of  the  next  ones.  This  gives  a  water-tight  roof  without 
cement.  They  cost  more. 


Fig.   1 6. — Section  of  roof  showing  modern  Spanish  tile,  cresting,  hip  rolls  and 
finials.     (Akron  Roofing  Tile  Company.) 

The  common  Spanish  S  tile  are  usually  made  on  auger  machine. 
They  are  n  inches  wide  and  12  inches  long,  with  extreme 
height  of  roll  of  3  inches,  and  weigh  800  to  900  pounds  per 
square. 

The  interlocking  Spanish  look  like  common  Spanish  tiles,  and 
while  they  have  side  and  end  locks,  these  do  not  show  on  roof. 
They  are  usually  9  by  12  inches,  and  weigh  about  850  pounds 
per  square. 

Interlocking  Tile.  These  are  constructed  with  tongues  and 
grooves  on  the  edges  and  ends,  which  fit  into  each  other  and  lock 
the  tile  together. 

The  normal  interlocking  tile  are  usually  of  rectangular  outline, 
and  varying  size,  but  9  by  16  inches  are  common  dimensions. 

They  overlap  about  two  inches  on  all  sides,  and  about  135  are 
required  to  a  square.  The  weight  of  this  quantity  is  from  800 
to  850  pounds. 

Interlocking  shingle  tile  are  usually  9  by  13  by  ^  inches,  re- 
quiring about  190  per  square,  with  a  weight  of  800  to  900  pounds. 

Interlocking  Spanish  tiles  look  like  the  common  Spanish  tiles. 
They  have  side  and  end  locks,  but  these  do  not  show  on  the  roof. 


352  BUILDING  STONES  AND   CLAY-PRODUCTS 

They  are  commonly  9  by  12  inches  in  size,  and  weigh  about 
850  pounds  to  the  square. 

Materials  and  Manufacture.  The  crushing  and  preparation 
of  the  clay  are  done  by  methods  which  are,  in  general,  similar  to 
those  employed  for  pressed-brick  manufacture,  but  the  grinding 
and  preparation  of  the  clay  are  more  carefully  done. 

Shingle  and  Spanish  tile  (except  the  Old  Spanish)  can  be  made 
by  forcing  a  ribbon  of  clay  from  an  auger  machine,  but  inter- 
locking tile  are  manufactured  by  repressing  slabs  of  the  tempered 
clay  in  a  special  form  of  machine. 

The  tile  are  then  carefully  dried  and  burned.  If  the  setting  of 
the  tile  in  the  kiln  and  the  burning  are  not  properly  done,  there 
is  great  liability  to  loss  from  warping,  cracking  and  checking. 

A  softer  burned  tile  costs  less  to  manufacture  and  is  a  better 
non-conductor  of  heat,  as  well  as  providing  a  cooler  roof. 

Owing  to  our  more  severe  winters,  American  tile  should  be 
fairly  hard  burned. 

Porosity  of  Roofing  Tile.  There  exists  a  diversity  of  opinions 
regarding  the  relative  merits  of  porous  and  vitrified  tile.  Most 
French  and  German  ones  are  porous;  so,  too,  are  some  American 
ones. 

Tests  made  by  H.  A.  Wheeler1  show  that  the  absorption  of 
well- tested  American  roofing  tile  ranges  from  i  to  21  per  cent 
after  24  hours'  immersion,  but  that  there  is  no  fixed  relation 
between  absorption  and  frost  resistance. 

These  absorption  percentages  are  shown  in  the  accompanying 
table  (p.  355). 

The  objections  urged  against  a  porous  tile  are :  i .  That  they 
lack  frost  resistance.  2.  They  absorb  dirt  and  become  old  and 
unsightly  looking  in  a  short  time.  3.  That  high  absorption  of 
water  increases  weight  of  roof,  but  if  25  per  cent  is  absorbed 
and  this  overloads  the  roof  it  means  too  small  a  safety  factor. 
4.  They  may  contain  soluble  salts,  which  sometimes  cause  the 
tile  to  disintegrate.  The  objections  urged  against  a  vitrified  tile 
are  that  it  tends  to  condense  moisture  on  its  under  surface,  if 
laid  with  the  under  surface  exposed.  But  vitrified  tile  are  not 

1  American  Ceramic  Society,  Transactions,  VIII,  p.  154,  1906. 


Regular  Tile 


Flat  Top 
Flattened  tile  for  finishing  course. 


Right  Gable  Rake 

Depth  of  flange  below  top  of  sheathing,  one  inch. 
Weight  per  foot,  6  pounds. 


End  Band 

Same  length  as  regular  tile;  roll  only. 
Used  for  flashing  purposes. 


Closed  Eave. 
Inverted  tile  showing  fixed  closure. 


Hip  Roll. 


Gable  Terminal. 


Two-way  Terminal. 


PLATE  LVI. — Regular  and  special  shapes  of  Spanish  interlocking  tile. 
(Ludovici  Roofing  Tile  Company.) 

353 


ROOFING  TILE 


355 


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356  BUILDING  STONES  AND   CLAY-PRODUCTS 

necessarily  more  durable  than  porous  ones  and  much  may- depend 
on  the  size  of  the  pores.  Thus,  it  is  argued  that  large  pores,  with 
thin  walls  between,  do  not  resist  the  internal  pressure  of  freezing 
water  as  well  as  evenly  distributed,  thicker  walled,  smaller  pores. 

Some  claim  that  porous  tile  should  not  be  laid  against  brick- 
work, as  they  absorb  the  moisture  from  the  brick  backing. 

There  has  been  some  discussion  as  to  the  value  of  glazing 
roofing  tile,  and  it  may  be  said,  by  way  of  preface,  that  where 
such  a  coat  is  given  to  the  tile  for  the  purpose  of  covering  up 
certain  bad  features  or  prolonging  its  life  the  practice  is  a  very 
bad  one. 

On  the  other  hand,  if  the  tile  is  coated  for  the  purpose  of  add- 
ing to  its  architectural  beauty,  then  the  object  is  a  praiseworthy 
one.  The  last,  however,  opens  up  a  great  opportunity  of  which 
American  architects  have  as  yet  taken  very  little  advantage. 

But,  whatever  the  reason  for  applying  it,  the  glaze  should  be 
durable. 

Roofing  tile  may  be  covered  with  either  a  slip  or  a  true  glaze. 

The  slip  is  usually  a  natural  clay  which  in  burning  becomes 
converted  to  an  impervious  coat  that  may  be  either  vitrified  or 
dull.  It  may  be  used  to  give  the  surface  of  the  tile  either  a 
better  color,  or  a  cleaner  and  smoother  surface. 

Where  a  roofing  tile  is  made  from  a  clay  that  burns  light  pink, 
buff  or  greenish  color,  it  is  necessary  to  use  a  slip  to  hide  the 
unsightly  color  of  the  body.  This  practice  is  objectionable,  for 
if  the  surface  of  the  ware  is  chipped  the  body  color  becomes 
exposed.  A  tile  with  much  scum  does  not  take  a  slip  well,  and 
the  latter  scales  off  on  freezing. 

Slips  could  be  artificially  colored  and  afford  the  architect 
excellent  opportunity  for  polychrome  design,  which  is  becoming 
of  such  importance  in  modern  terra-cotta  work.  Little  or  none 
of  this  is  done  in  the  United  States. 

The  glazes  used  on  roofing  tile  may  be  either  matt  or  bright. 
The  former  are  mostly  used,  the  latter  being  objectionable  be- 
cause of  the  strong  light  reflection  from  them. 

The  relative  advantages  of  slip  and  glazed  tile  include  the 
following. 


PLATE  LVII,  Fig.  i.  —Interlocking  tile  showing  obverse  (A)  and  reverse  (B)  side. 

(U.  S.  Roofing  Tile  Co.) 


PLATE  LVII,  Fig.  2.  —Molding  30-inch  sewer  pipe  in  pipe  press. 

357 


ROOFING  TILE  359 

Slip  coats  are  easier  to  produce  and  subject  to  fewer  defects 
than  glazes. 

A  slip  is  thought  by  some  to  prove  more  durable  on  a  porous 
tile  than  a  glaze. 

Slip  coatings,  being  duller  than  even  a  matt  glaze,  cause  the 
minimum  of  reflection. 

Glazed  tiles  possess  an  impervious  surface,  which  slip-coated 
tiles  do  not,  hence  are  less  liable  to  discolor  with  soot  or  dirty 
water.  A  glazed  tile  can  be  scrubbed  clean  easier  than  a  slip- 
coated  one. 

A  glaze,  it  is  true,  may  keep  water  out  of  a  porous  tile  body, 
but  if  the  latter  is  glazed  only  on  the  upper  surface  it  may  absorb 
moisture  from  the  under  side. 

Requisite  Characters  of  Roofing  Tile.  The  following  may  be 
tentatively  cited:  i.  Hard  body.  2.  Low  absorption,  say, 
under  10  per  cent.  3.  Freedom  from  warping.  4.  Absence  of 
soluble  salts.  5.  Good  ring  when  struck.  6.  Frost  resistance. 

Tests  of  Roofing  Tile.  It  is  doubtful  if  any  are  made  even  by 
engineers  or  architects,  however  important  they  may  be;  indeed, 
the  main  selling  requirement  very  often  and  unfortunately  is 
color  and  shape.  The  following  would  seem  to  be  important 
tests. 

1.  Frost  Resistance.     Vitrified  tile  should  rate  high  on  this 
test. 

2.  Soluble  Salts.     These  may  be  present  in  porous  tile,  and  if 
present  in  sufficient  quantity  have  been  known  to  cause  serious 
disintegration  of  the  tile. 

3.  Transverse  Strength.    Some  advocate  a  cross-breaking  test. 

4.  Permeability  Test.     This  may  be  carried  out  as  follows: 
Paint  the  tile  on  all  faces,  except  one,  and  a  portion  of  the  oppo- 
site one,  with  a  waterproof  shellac  or  varnish.     The  partially 
covered  face  is  then  fitted  with  a  glass  tube  8  inches  high  and 
if  inches  in  diameter,  and  fastened  with  a  little  cement.     Keep 
this  cylinder  filled  with  water  to  a  constant  level,  adding  water 
from  time  to  time  as  it  is  absorbed  by  the   tile.     The   time 
required   for  the  water  to  pass  through  to  the  lower  side  is 
measured. 


360  BUILDING"  STONES  AND   CLAY-PRODUCTS 

But,  after  all,  the  actual  selling  requirements  are  often  color 
and  shape,  which  are  largely  matters  of  personal  taste  of  the 
architect. 

The  slow  absorption  of  roofing  tile  in  this  country  has  been  due 
to  the  excessive  cost,  which  ranges  from  $8.00  to  $50.00  per  square, 
depending  on  pattern,  whether  glazed  or  not,  and  other  factors. 
They  have  also  had  to  compete  with  other  forms  of  roof  covering, 
such  as  wood  shingles,  slate,  metal  roofing,  asbestos,  slabs,  etc. 

Miscellaneous  Clay  Slabs,  used  for  Roofing  Purposes.  In 
addition  to  the  regular  roofing  tile,  book  tiles  are  sometimes  em- 
ployed. They  rest  on  tee  irons,  and  are  sometimes  used  for  a 
pitch  roof  and  covered  with  slate.  An  objection  raised  against 
them  is  that  they  lack  strength  against  shock  and  load. 

Another  form  of  product  sometimes  used  on  roofs  is  a  rabbeted 
block  having  rabbeted  edges  on  two  sides,  to  permit  the  block  to 
set  down  between  the  tee  irons  on  which  it  rests.  These  blocks 
may  be  either  solid  or  hollow,  and  made  of  either  porous  or  hard 
burned  material.  They  commonly  have  a  width  of  12  inches, 
and  a  length  of  10  to  24  inches.  The  common  thicknesses  are 
2,  2^,  3  and  4  inches.  The  2-inch  blocks  are  said  to  weigh  about 
12  pounds  per  square  foot;  the  3-inch,  14  pounds;  and  the  4-inch, 
18  pounds. 

Quarry  tile,  viz.,  red  burning,  square  or  rectangular  slabs, 
f  to  i  inch  in  thickness,  are  often  used,  especially  for  flat  roofs, 
which  serve  for  gardens  or  are  continually  being  walked  over. 
They  are  sometimes  salt  glazed.  These  quarries  sell  for  about 
$18.00  to  $30.00  per  1000  at  New  York. 

Special  Shapes.  The  body  of  a  roof  is  covered  with  stock 
tile,  but  there  are  many  different  shapes 
made  which  are  employed  for  trimmings, 
and  to  connect  different  parts  of  the  roof 
surface  which  do  not  agree  in  slope  or 
continuity. 

The  following  shapes  may  be  men- 
tioned: 

Fig.  17.  -Quarry  tile.  mp  ^   yalky   r^       These  ^  ^ 

cut  to  fit  the  angles  of  the  hips  or  valleys.     Most  tiles  have  to 


ROOFING  TILE  361 

be  cut  in  their  unburned  condition,  but  soft  tile  can  sometimes 
be  cut  on  the  job.  Each  hip  or  valley  requires  both  " lefts" 
and  "  rights."  This  work,  done  at  the  factory,  is  charged  for  by 
the  running  foot. 

"  Closed  "  Hip  and  Valley  Tile.  These  have  a  closed  end  to 
prevent  snow  or  rain  from  blowing  up  underneath  them. 

Ridge  and  Eave  Tile.  Spanish  and  interlocking  tile  need  a 
special  starting  tile  at  eave  line  and  a  finishing  tile  at  ridge,  to 
make  a  tight  roof  and  one  of  good  appearance.  The  eave  tile 
has  a  closed  end  and  is  made  in  a  press  with  special  mold.  Ridge 
tile  differ  from  the  regular  ones,  in  having  the  upper  half  flat- 
tened to  a  plane,  which  rests  on  the  sheathing  boards,  and  has 
its  upper  edge  covered  by  a  finishing  tile.  The  ridge  tile  are 
molded  in  presses. 

Hip  Rolls  and  Cresting.  These  are  pieces  of  curved  or  other 
shape  to  fit  over  the  ridges  and  hips,  and  make  the  roof  weather- 
tight.  They  are  sometimes  of  very  ornamental  character.  The 
molding  is  done  by  hand  or  machine  power,  usually  in  plaster  dies. 

Hip  Roll  Starter.  This  is  a 
closed-end  tile  placed  at  the 
lower  end  of  the  hip  of  the  roof, 
and  can  be  made  quite  orna- 
mental in  its  character. 

Finials.  These  are  orna- 
mental pieces  used  for  finishing 
off  the  joining  of  the  ridge  line 
with  the  hips,  ridge  line  at 
gables,  or  top  of  a  tower.  They 
are  often  highly  ornamental  and  Fis-  l8-  ~  Finials  for  tile  roof- 

„  J,  .,    ,  ,       ,  (Akron  Roofing  Tile  Co.) 

are  usually  modelled  by  hand. 

Graduated  or  Tower  Tile.  Special  shapes  are  necessary  to 
fit  the  converging  lines  of  a  tower  with  pyramidal  or  dome-shaped 
roof,  for  it  will  be  readily  understood  that  as  we  go  from  the 
bottom  to  the  top  of  such  a  tower  the  tiles  diminish  in  width. 

The  rates  at  which  the  tiles  diminish  in  width  are  quite  differ- 
ent. Thus,  those  made  for  a  ten-foot  tower  cannot  be  used  for  a 
twenty-five  foot  tower.  This  means  that  new  molds  and  dies 


362  BUILDING   STONES  AND   CLAY-PRODUCTS 

must  be  made  for  almost  every  job.  Tiles  from  a  fourteen- 
foot  tower  can  sometimes  be  shifted  to  a  fifteen  or  sixteen-foot 
one,  this  being  more  easily  done  with  Spanish  tiles  than  with 
interlocking  ones. 


Fig.  19.  —  Graduated  tower  tile.    Spanish  pattern. 


CHAPTER  XIII 
WALL  AND   FLOOR  TILE. 

TILE  for  interior  work  have  been  used  since  an  early  date, 
first  in  the  far  East,  later  on  in  Europe,  their  combined  use  for 
beauty,  durable  linings  and  clean  surface  being  well  recognized. 
Though  used  first  in  the  Western  countries  during  the  twentieth 
century  mainly  for  bathrooms,  the  rich  decorative  effects  pro- 
ducible have  given  them  a  more  extended  field  of  usefulness  in 
mantels,  vestibules  and  other  locations. 

Tile  can  be  divided  into  two  groups,  floor  tile  and  wall  tile. 
The  former  are  hard  burned,  dense  (sometimes  nearly  non- 
absorbent)  and  not  usually  glazed.  The  latter  are  quite 
absorbent  and  covered  with  some  sort  of  glaze. 

Manufacture  of  Wall  Tile.  Wall  tile  may  be  made  of  clay 
alone,  or  of  a  mixture  of  clays,  flint  and  feldspar.  Those  with  a 
white  body  are  always  of  this  character. 

The  raw  materials  are  first  purified  1  by  mixing  with  water 
to  a  thin  cream,  and  then  straining  through  a  silk  screen  of 
about  1 20  meshes  to  the  linear  inch.  This  is  then  run  into  filter 
presses  and  the  water  squeezed  out.  If  plastic  tile  are  made  the 
clay,  after  some  kneading,  is  ready  for  use,  but  in  making  dust- 
pressed  tile,  —  and  the  bulk  of  modern  tile  are  such,  —  the  clay 
has  to  be  dried,  crushed  to  powder  and  steamed  in  order  to  render 
it  slightly  moist.  This  powdered  moist  clay  is  stored  until  used. 
The  tile  are  formed  in  a  tile  press,  which  consists  essentially  of  a 
steel  box,  with  rising  bottom,  and  a  screw  plunger.  Its  action 
is  similar  to  that  of  a  dry-press  brick  machine,  but  the  shape  of 
the  tile  is  governed  by  that  of  the  plunger  or  bottom  of  the  box, 
and  embossments  can  be  made  by  shaping  these  to  the  required 

1  Wall  tile  made  by  the  plastic  process  are  sometimes  made  from  unwashed 
clays. 

363 


364  BUILDING  STONES  AND   CLAY-PRODUCTS 

design.  Thus,  moldings  and  other  ornamental  patterns  are 
produced  or  a  tile  with  decoration  in  relief  is  pressed. 

The  tile  after  pressing  are  set  in  saggers  or  fire-clay  boxes, 
which  are  piled  one  upon  another,  thus  protecting  their  contents 
from  the  action  of  the  flames.  After  burning  at  the  proper  tem- 
perature, the  tile  are  sorted  and  the  glaze  applied.  Transparent 
glazes  are  mostly  mixtures  of  silicate  of  lead,  lime,  potash  and 
alumina,  the  mixture  being  ground  in  water  to  form  a  thin 
cream,  in  which  the  face  of  the  tile  is  dipped. 

Coloring  matter,  if  added,  is  introduced  in  the  form  of  metallic 
oxides,  cobalt  for  blue,  copper  for  green,  iron  for  yellow  and 
light  brown,  and  manganese  for  dark  brown,  or  by  mingling 
these  a  variety  of  shades  is  obtainable.  The  flowing  of  the 
glaze  in  the  second  firing,  which  the  tile  now  receives,  may 
cause  a  variation  in  its  thickness,  resulting  in  lighter  and  darker 
tones. 

Matt  or  dull  glazes  are  of  different  composition  and  mani- 
pulation, and  are  much  used  now.  They  are  colored  in  the 
same  way  as  the  clear  glazes,  but  the  texture  depends  on  a  thick 
coat  of  the  material  being  applied  to  the  tile,  which  also  makes 
possible  certain  schemes  of  decoration  not  possible  in  bright 
glazes.  Matt  glazes  are  applied  by  dipping  or  with  a  brush. 
Some  wondrous  effects  in  colored  glazes  and  crystalline  glazes 
have  been  produced  by  modern  manufacturers,  both  in  the 
United  States  and  Europe. 

Dust-pressed  tile  are  easily  made,  and  quite  straight,  but  on 
this  account  they  are  thought  by  many  to  exhibit  a  hard  and 
unsympathetic  surface,  and  hence  many  prefer  the  plastic  tile, 
which  permit  a  freer  treatment  of  the  clay. 

These  plastic  tile  are  molded  from  soft  clay,  with  some  non- 
plastic  materials  as  ground  burned  clay  added.  They  are 
formed  by  hand  pressure  in  plaster  molds,  these  being  larger 
than  the  size  desired  in  the  tile  to  allow  for  shrinkage  in 
burning. 

If  the  surface  is  to  be  embossed  it  can  be  done  in  the  molding, 
by  having  the  inner  surface  of  the  mold  bear  the  embossment  in 
reverse,  or  the  tile,  after  drying  sufficiently  to  shrink  away  from 


WALL  AND   FLOOR  TILE  365 

the  mold,  can  be  removed  and  the  modeled  embossment  worked 
out  by  hand.  Plastic  tile  are  not  always  glazed. 

Glazes  should  be  free  from  blisters,  bubbles,  or  holes,  and 
should  not  crack  or  "  craze."  The  latter  may  not  appear  at 
once.  Moreover,  even  if  the  tile  is  free  from  "  crazes  "  when 
placed  in  the  wall,  these  may  be  caused  by  the  cement  in  which 
the  tile  is  laid,  or  by  faulty  composition  of  the  glaze. 

Wall  tile  when  dust  pressed  are  made  in  square  or  rectangular 
shapes.  Glazed  wall  tile  are  made  in  the*  following  sizes,  6  by  6 
inches,  6  by  3  inches,  6  by  2  inches,  4!  by  4^  inches,  4!  by  2! 
inches,  also  in  special  sizes  9  by  3  inches,  and  9  by  4^  inches. 
Though  the  design  or  single  panel  may  be  large,  it  is  customary 
to  make  it  up  of  a  number  of  smaller  pieces,  as  large  ones  would 
have  a  tendency  to  warp  in  the  fire. 

The  use  of  wall  tile  has  been  well  set  forth  by  Charles  F.  Binns, 
who  writes  that  "  It  is  not  necessary  to  point  out  the  advantage 
of  glazed  tile  in  bathrooms,  light  shafts  and  underground  offices. 
These  are  things  of  the  past  and  are  sufficiently  obvious.  A  new 
day  is  dawning,  however,  in  the  use  of  ceramic  decorations  and 
in  its  advance  there  will  be  revealed  possibilities  at  present 
imperceived." 

They  can  be  artistically  used  in  places  where  wood  and  plaster 
were  formerly  exclusively  employed.  "  Not  only  may  a  wainscot 
or  frieze  be  filled  with  richly-toned  tile  glazed  in  a  delicate  tex- 
ture matt,  but  panels,  arches,  and  ceilings  may  be  similarly 
treated.  Such  a  surface  is  not  only  structurally  sound  and 
artistic,  but  perfectly  sanitary,  for  the  whole  room  may  be 
washed  without  damage." 

Properties  of  Floor  Tile.  Under  this  heading  are  included  tile 
of  a  variety  of  shapes  and  colors  which  are  used  for  flooring. 

On  account  of  the  conditions  under  which  they  are  used  they 
should  possess  sufficient  hardness  to  resist  abrasive  action,  suffi- 
cient transverse  strength  to  resist  knocks  and  sufficient  density 
to  prevent  absorption  of  water  and  dirt.  It  would  be  preferable 
if  all  were  non-absorbent,  but  they  are  not. 

The  following  figures  will  give  the  range  of  absorption  per- 
centages determined  on  a  number  of  New  Jersey  tiles: 


366  BUILDING  STONES  AND   CLAY-PRODUCTS 

ABSORPTION  OF  NEW  JERSEY  FLOOR  TILE. 

Color.  Per  cent  absorption. 


0-3.59 
White  .............................................          Q-.03I 

Red  ..............................................      1.30-3.11 

Pink  ...............................................  8-3.70 

Red  brown  ........................................        3.8-4.7 

Buff  ..............................................        1.7-3.3 

Green  .............................................        1.6-6.63 

Black  ----  ......................................  ...  0-5.39 

Gray  .............................................  o-.s 

Method  of  Manufacture.  Great  care  is  necessary  in  the  selec- 
tion and  mixing  of  the  raw  materials,  and  the  manufacturer  must 
adjust  his  mixtures  for  the  face  of  the  tile  and  the  backing  in  case 
they  are  different.  Clay  used  for  floor  tile  should  be  as  free 
from  soluble  salts  as  those  employed  for  the  manufacture  of 
pressed  brick  or  terra  cotta,  although  the  soluble  salts  may  come 
from  the  coloring  materials  used.  Floor  tile,  when  white,  are 
commonly  made  of  a  mixture  of  white-burning  clays,  flint,  and 
feldspar.  Buff-colored  tiles  and  artificially  colored  ones  are 
usually  made  from  fire  clays,  while  red  tiles  are  often  made  from 
red-burning  clay  or  shale. 

Floor  tiles  are  nearly  always  molded  by  the  dry-press  process 
in  hand-power  machines.  The  tile  are  placed  in  saggers  in  the 
kiln  for  burning,  and  since  there  is  in  most  cases  no  glaze  only 
one  firing  is  necessary. 

Floor  tile  may  be  divided  into  plain  and  encaustic. 

The  plain  tile  are  made  of  one  clay  throughout.  Those 
recognized  are  the  mosaics,  which  are  J  inch  thick  and  J  inch 
square  and  fastened  to  paper  sheets.  Other  sizes  are  f  inch 
square,  f  inch  hexagon,  i  inch  hexagon,  yf  inch  circle.  The 
plain  ones  may  be  vitreous  or  semi-  vitreous. 

Large  tile,  known  as  quarry  tile,  6  and  8  or  more  inches  square, 
f  to  i  inch  thick,  and  of  red  color,  are  much  used  now  for  flooring. 

In  recent  years  floor  tile  with  a  matt  glaze  have  been  occa- 
sionally employed,  but  their  appropriateness  for  flooring  is 
questionable,  as  the  surface  coating  is  likely  to  become  cracked 
or  chipped  or  worn  off. 


PLATE  LVIII.  —  Encaustic  tile.    The  design  is  superficial. 


367 


WALL  AND  FLOOR  TILE  369 

Encaustic  tiles  have  a  facing  of  one  kind  of  clay  and  a  back- 
ing of  another.  Those  which  have  a  design  of  several  colors  are 
formed  with  the  aid  of  a  brass  cell  frame,  of  the  same  depth  as 
the  mold  box  used,  and  which  consists  of  a  framework  of  brass 
strips  arranged  so  as  to  form  the  outline  of  the  colors  making 
the  pattern.  The  framework  is  placed  in  the  mold  and  the 
colored  clays  sifted  into  their  proper  divisions.  This  is  done  by 
using  a  sieve  so  perforated  as  to  expose  only  certain  cells,  and 
filling  the  exposed  cells  with  facing  mixture  of  the  desired 
color.  This  means,  of  course,  that  it  is  necessary  to  use  as 
many  sieves  as  there  are  colors  in  the  design.  When  all  the 
colors  are  filled  in  the  cell  frame  is  lifted  out  and  the  mold 
filled  with  the  clay  backing. 

Encaustic  tile  have  for  their  base  buff  and  red-burning  clay. 
Since  the  iron  in  these  is  mainly  present  as  free  oxide  it  is  im- 
possible to  burn  such  tiles  to  vitrification  without  destroying 
the  color. 

Tests  of  Wall  Tile.  Here,  again,  we  have  no  standard  series  of 
tests,  but  those  applied  to  enameled  brick  may  be  regarded  as 
about  equally  applicable  to  wall  tile. 

Tests  of  Floor  Tile.  The  condition  of  use  to  which  floor 
tile  are  subjected  will  no  doubt  suggest  the  tests  which 
should  be  made  upon  them.  The  tests  which  the  writer 
suggests  are : 

1.  Determination  of  abrasive  resistance  in  order  to  find  out 
the  rate  and  amount  of  ware  under  rubbing  action. 

2.  Transverse  test  to  determine  the  resistance  of  the  tile  to 
blows  and  the  pressure  of  heavy  weights. 

3.  Absorption.     Tile  of  high  absorptive  power  are  undesir- 
able as  they  soak  up  water  and  dirt. 

4.  Hardness.     They  should  have  a  hardness  of  not  less  than 
6  or  7. 

5.  Unfortunately,  there  are  no  accepted  standards  of  com- 
parison with  which  the  first  three  sets  can  be  checked  up. 

The  following  tests  were  made  at  the  Watertown,  Mass.,  Arse- 
nal in  1894,  on  specimens  supplied  by  the  American  Encaustic 
Tiling  Co.,  Ltd.  The  tile  were  tested  on  edge. 


370 


BUILDING   STONES  AND   CLAY-PRODUCTS 


Name  and  color. 

Dimensions. 

Sec- 
tional 
area, 
sq.  in. 

First 
crack, 
Ibs. 

Ultimate  strength. 

Per  cent 
absorp- 
tion by 
weight. 

Height, 
inches. 

Compressed 
surface, 
inches. 

Total 
Ibs. 

Per  sq. 
in.,  Ibs. 

i.   Buff  
2.    Salmon  
3.   Light  gray 

3.oo 
•  98 
.98 
•  99 

.00 

.98 
.98 
-97 
.00 
99 
-99 
2.99 
3.oi 
2.99 
2.99 
2-99 
(  6.00 
]5.98 
(5-99 
2.98 
3.00 

3  oo 
2.98 
2.98 
2.99 
3.oo 
2.98 
2.98 
2.98 
3.oo 
3.oo 
2.99 
2-99 
3.oi 
2.99 
2.99 
2.99 
6.00 
5-99 
6.00 
5-96 
5-99 

.46 
•  44 
.46 
.46 
.49 
.46 
•  47 
-46 
.48 
-48 
-49 
•  49 
.50 
-50 
•  49 
•  47 
.58 
-57 
.58 
-33 
-33 

•  344 
.275 
•  335 
.389 
•  434 
-335 
.365 
.335 
.404 
.404 
.429 
.429 
-469 
•  459 
.429 
-369 
.480 
.414 
.480 
.967 
.977 

26,900 
25,800 
27,300 
26,800 
23,200 
29,100 
22,700 
22,700 
3,100 
15,400 
3,400 
4,700 
2,400 
20,400 
45,5oo 

3,200 

97,300 
43,ooo 
54,8oo 

10.100 

7,800 

30,610 
53,5oo 
65,100 
47,700 
35,650 
47,36o 
24,200 
24,600 
26,880 
65,800 
48,100 
42,700 
72,900 
25,700 
45,750 
27,800 
173,200 
167,800 
213,200 
I7,5oo 
24,860 

22,775 
41,961 
48,764 
35,263 
24,860 
35,475 
17,729 
18,427 
19,145 
46,866 
33,66o 
29,881 
49,625 
I7,6l5 
32,015 
20,307 
49,770 
49J50 
61,264 
8,897 
12,575 

5-9 

2.8 

3.1 

2.1 

3.2 

2.1 
9-9 

"'!o6' 
o 

.06 

.12 
.23 
.12 
.04 
•  05 
.06 
14.2 
12.3 

4-    Dark  gray  
5.   Red..  . 

6.   Chocolate  

7.   Black.  .  . 
7-   Black  
8.   White  bisque  
8.   White  vitrified  
9.    Silver  gray  vitrified  .  . 
10.   Pink  
ii.   Celadon  
12.   Light  blue... 

13.    Dark  blue  
14.   Green  
15.) 
16.  >  Alhambra  
17.) 
18.    Glazed  white  .  . 

19.   Glazed  ivory  

A  series  of  tests  made  to  determine  the  wearing  qualities  of 
flooring  materials  was  published  in  the  Scientific  American  for 
July  3,  1897.  They  are  of  interest  as  showing  the  comparative 
wearing  qualities  of  floor  tile  and  other  materials  used  for  the 
same  purpose.  The  following  statements  are  quoted  from  this 
article.  The  materials  tested  were  rubber  tile,  English  earthen- 
ware tile,  Vermont  marble,  marble  mosaic,  flagstone,  Oregon 
pine,  teak  wood,  white  pine  and  oak.  The  experiments  were 
carried  out  by  Messrs.  William  Gray  &  Sons,  and  were  made 
under  the  careful  supervision  of  Mr.  William  J.  Gray. 

In  carrying  out  the  tests  the  specimens  were  cemented  to  iden- 
tical blocks  of  sandstone,  each  of  which  weighed  twenty-one 
pounds.  The  samples  represented  a  surface  six  inches  square, 
and  the  thickness  of  each  sample  was  the  same  as  that  commonly 
used  in  the  various  floorings.  The  interlocking  rubber  tile  speci- 
men was  f  inch  thick,  the  No.  i  Vermont  marble  was  i  inch 
thick,  the  Oregon  pine  2\  inches  thick,  and  so  on. 

The  samples  were  all  placed  face  downward  upon  a  horizontal 
iron  rubbing  wheel  10  feet  in  diameter,  which  was  run  for  a 
period  of  one  hour  at  a  speed  of  75  revolutions  per  minute.  A 
suitable  frame  held  the  blocks  loosely  in  place  and  prevented 


WALL  AND   FLOOR  TILE  371 

them  from  rotating  with  the  wheel,  care  being  taken  to  let  the 
full  weight  of  the  blocks  bear  upon  the  wheel.  The  face  of  the 
wheel  was  freely  supplied  during  the  test  with  the  best  sharp 
rubbing  sand  and  water. 

The  results  were  full  of  surprises.  By  far  the  best  showing  was 
that  made  by  the  interlocking  rubber  tile,  which  only  lost  g*$ 
inch  as  the  result  of  an  hour's  grinding.  On  the  other  hand, 
the  marble  mosaic  collapsed  altogether,  the  one-inch  strip  being 
rubbed  entirely  away  within  fifteen  minutes  under  a  pressure 
of  a  little  over  half  a  pound  to  the  square  inch.  The  whole  slab 
disappeared  in  thirty-five  minutes  under  the  same  pressure. 

Next  to  the  rubber,  the  English  earthen  tile  showed  by  far 
the  best  results,  losing  only  f  inch  in  thickness;  and  of  the 
stones,  the  granolithic  made  the  best  showing,  losing  f  inch, 
flagstone  coming  next  with  y9g  inch  wear.  The  marbles  wore 
away  very  fast,  No.  i  Vermont  marble  losing  f  of  an  inch. 
Their  average  resistance,  indeed,  was  not  as  high  as  that  of  the 
woods. 

One  of  the  most  curious  results  is  shown  in  the  action  of  the 
woods,  where  teak  lost  nearly  double  as  much  as  the  softer  white 
pine,  the  wear  being  respectively  ^f  and  -£$  of  an  inch.  Yellow 
pine  showed  the  same  wear  as  white  pine,  and  the  oak  specimen 
lost  the  same  amount  as  its  great  rival  Oregon  pine,  which  was 
reduced  by  f  inch. 


CHAPTER  XIV. 
SEWER  PIPE. 

Raw  Materials.  This  class  of  ware,  which  is  sometimes  called 
sanitary  pipe,  is  made  from  a  clay  or  shale,  or  mixture  of  two  or 
more  kinds  of  these  materials,  whose  physical  properties  are 
such  that  they  will  either  burn  to  a  vitrified  body  or  one  of  low 
absorption  and  also  take  a  salt  glaze.  In  some  sewer-pipe  mix- 
tures a  fire  clay  is  used  as  one  of  the  ingredients,  in  others  only 
non-refractory  clays  are  employed. 

Manufacture.  Sewer-pipe  clays  are  thoroughly  ground  if 
necessary,  well  mixed  and  then  molded  in  a  special  form  of  press, 
from  which  the  clay  issues  through  a  die  of  the  proper  form. 
Special  shapes,  such  as  traps,  sockets  and  elbows,  are  usually 
made  by  hand  in  plaster  molds  and  require  careful  drying.  At 
times  Y  shapes  are  made  by  cutting  one  straight  piece  on  the 
slant  and  joining  it  onto  a  pipe  with  wet  clay.  T's  are  made  in 
a  similar  manner. 

Sewer-pipe  are  slowly  dried  on  slatted  floors,  heated  by  steam 
pipes,  and  burned  in  down-draft  kilns.  When  the  kiln  has 
reached  a  temperature  of  not  less  than  1150°  C.,  salt  is  thrown 
into  the  fires  and  the  sodium  vapors  passing  through  the  kiln, 
unite  with  the  clay,  forming  a  glaze  on  the  surface  of  the  ware 
known  as  a  "  salt  glaze."  Many  clays  are  capable  of  taking  a 
good  salt  glaze,  but  some  take  a  poor  one,  and  others  do  not 
glaze  at  all.  A  poor  salt  glaze  might  be  due  to  the  character  of 
the  raw  material,  too  low  temperature  of  burning,  or  the  latter 
combined  with  presence  of  an  excess  of  soluble  salts. 

A  sewer  pipe  is  sometimes  glazed  with  an  easily  fusible  clay, 
known  as  a  "  slip  clay."  This  is  applied  to  the  surface  of  the 
pipe  previous  to  burning  and  melts  to  a  glassy  coat  at  the  tem- 
perature of  firing.  This  practice  has  been  abandoned  in  the 

372 


SEWER  PIPE 


373 


United  States,  as  the  salt  glaze  is  cheaper  and  equally  satis- 
factory. Sewer  pipes  are  made  in  diameters  from  3  up  to  36 
inches. 

The  following  table  of  data,  taken  from  the  catalogue  of  one 
large  manufacturer,  may  be  of  interest: 


Inside  diameter, 
inches 

Weight  per  foot  in 
pounds 

Area  in  inches 

No.  of  feet  in  average 
car  load  . . 


Thickness  in  inches  . . 


3 

7-5 

7 

3400 


4 

IO 

12 
2600  2000 


16.5 
28 


1599 


IOOO  QOO 


28 


64 


12 

39 

113 


15 

58 

177 


750  600  400  300 
It 


21 

105 


254  345 


240 
if 


125 


190 


140 


390  455 


1 80 
if 


The  following  data  of  a  somewhat  different  character  are  taken 
from  the  catalogue  of  another  company: 

APPROXIMATE  WEIGHTS,   DIMENSIONS,   ETC.,   STANDARD 
SEWER  PIPE. 


Calibre, 
inches. 

Thickness, 
inches. 

Weight  per  foot, 
pounds. 

Depth  of  sockets, 
inches. 

Annular  space, 
inches. 

2 

A 

5 

li 

1 

3 

i 

7 

l£ 

i 

4 

i 

9 

if 

f 

5 

f 

12 

if 

f 

6 

f 

15 

if 

f 

8 

f 

23 

2 

f 

9 

if 

28 

2 

f 

IO 

f 

35 

2* 

f 

12 

43 

2* 

1 

15 

1 

60 

2? 

i 

18 

i 

4 

85 

2f 

i 

20 

| 

IOO 

3 

i 

21 

I 

120 

3 

1 

22 

f 

130 

3 

I 

24 

f 

140 

3i 

i 

27 

2 

224 

4 

f 

30 

2| 

252 

4 

f 

33 

2j 

310 

5 

it 

36 

2* 

35° 

5 

"* 

374 


BUILDING   STONES  AND   CLAY-PRODUCTS 
DOUBLE   STRENGTH   PIPE. 


15 

tl 

75 

,, 

\ 

18 

if 

118 

2\ 

1 

20 

if 

138 

3 

| 

21 

if 

148 

3 

1 

22 

if 

157 

3 

i 

24 

2 

190 

3* 

| 

27 

2i 

265 

4 

1 

30 

2i 

290 

4 

1 

33 

2| 

335 

5 

i| 

36 

2| 

375 

5 

i.i 

Requisite  Qualities.  Sewer  pipe  should  be  free  from  pimples, 
blisters  and  cracks;  the  glaze  should  be  continuous  and  as 
smooth  as  possible;  the  pipe  should  be  straight  and  free 
from  cracks.  A  dark  color  is  preferred  by  most  engineers 
arid  architects. 

The  cause  of  the  defects  are  the  following: 

Blisters  may  be  due  to  air  imprisoned  in  the  clay  during  mold- 
ing. Surface  pimpling,  found  more  or  less  on  salt  glazed  pipe, 
appears  to  be  related  to  the  texture  of  the  body  and  treatment 
during  firing.  To  state  it  in  more  detail:  The  pimples  are 
caused  by  incipient  fusion,  bubbling  and  swelling  of  small  par- 
ticles of  shale,  or  perhaps  concretionary  matter  (such  as  pyrite 
and  limonite)  lying  close  to  the  surface.  They  can  be  prevented 
usually  by  finer  grinding  of  the  raw  material.  Rapid  burning 
seems  to  encourage  their  development.  Poor  glaze  may  be  due 
to  the  clay,  too  low  heat  in  firing  or  not  enough  salt. 

Warping  and  cracking  may  be  due  to  uneven  mixing,  uneven 
heating  or  inability  of  pipes  to  stand  weight  of  those  set  on 
top  of  them  in  the  kiln.  Fine  cracks  may  develop  in  the  drying 
and  open  still  further  in  the  burning. 

In  preparing  a  set  of  specifications  for  sewer-pipe  tests,  the 
committee  of  the  American  Society  for  Testing  Materials  has 
pointed  out  the  existence  of  the  following  demands.1 

.(a)  Strength.  This  includes  resistance  against  rupture,  homo- 
geneity of  the  material  and  the  vitrification  of  clay  pipe. 

1  Vol.  IX,  p.  263. 


Channel  Pipe 


.Socket   Pipe 


Running  Trap 


P  Trap 


PLATE  LIX.  —  Sewer  pipe  and  fittings. 


375 


SEWER  PIPE  377 

It  includes  also  the  necessary  data  for  the  thickness  of  shell 
and  the  importance  of  fire  cracks  in  vitrified  pipes. 

The  proper  requirements  should  be  stated  for  the  strength 
necessary  to  resist  crushing,  bursting  and  impact  under  various 
practical  conditions. 

(b)  Durability.    This  includes  resistance  to  wear  and  tear. 
There  should  be  given  the  required  resistance  against  abrasion 
by  sand  or  gravel  at  high  velocities  in  glazed  and  unglazed  pipes, 
the  density  or  specific  gravity  of  the  material  with  relation  to  its 
porosity  and  capillary  absorption  of  moisture. 

There  should  be  considered  the  corrosion  of  glazed  and  un- 
glazed vitrified  clay  pipes  by  acids,  alkalies,  steam,  frost  and 
gases. 

(c)  Serviceability.     This  relates  to  the  efficiency  of  the  pipes 
to  perform  the  best  service. 

Under  this  heading  should  be  considered  the  question  of 
smoothness,  the  glazing  of  vitrified  pipes,  blisters,  the  best 
sectional  form  for  various  purposes,  and  the  warping  of  pipes, 
including  the  permissible  deviation  from  true,  straight  pipes  and 
regular  curves  or  specials. 

The  best  lengths  of  the  individual  straight  pipes  and  specials 
should  be  determined. 

The  ends  of  pipes  with  reference  to  making  the  best  joints 
should  receive  most  careful  study  to  determine  the  best  practice 
for  different  conditions,  including  hub  and  spigot,  butt  and  collar, 
and  beveled  joints. 

All  specials,  such  as  branches,  spurs,  curves,  etc.,  should  re- 
ceive attention  with  reference  to  recommendations  as  to  size 
and  form. 

Specifications.  The  following  specifications  for  sewer  pipe  are 
given  by  Johnson  in  his  work  on  Engineering  Contracts  and 
Specifications. 

Straight  sections  are  termed  "pipes";  branches,  bends,  re- 
ducers, etc.,  are  fittings,  "  specials  "  or  special  pieces. 

All  hubs  or  sockets  should  be  of  sufficient  diameter  to  receive 
spigot  end  of  next  following  pipe  or  special  to  full  depth,  without 
chipping,  and  leave  J  inch  all  around  for  mortar. 


378  BUILDING   STONES  AND  CLAY-PRODUCTS 

In  the  case  of  pipes  and  specials  12  inches  and  upward  in 
diameter  at  least  40  per  cent  shall  be  truly  or  substantially  cir- 
cular. If  less  than  12  inches  in  diameter,  at  least  60  per  cent 
circular.  Of  those  that  are  not  circular  all  that  show  long 
diameter  more  than  from  6  to  7  per  cent  greater  than  short  one 
are  to  be  rejected.  Pipes  and  specials  showing  angles,  sharp 
curves  or  flat  curves  to  be  rejected. 

A  single  fire  crack  extending  through  whole  thickness  of  pipe 
must  not  be  more  than  two  inches  long  at  spigot  end  or  more  than 
one  inch  long  at  hub  end,  measured  from  shoulder  in  the  latter 
case.  Two  or  more  such  cracks  at  either  end  cause  rejection. 

A  single  fire  crack  extending  through  two-thirds  of  the  thick- 
ness of  pipe  must  not  be  over  four  inches  long.  Two  or  more 
such  cracks  cause  rejection. 

A  single  fire  crack  extending  through  one-half  of  the  thick- 
ness must  not  be  over  6  inches  long.  Two  or  more  cause  rejection 
of  the  pipe. 

A  single  fire  crack  extending  through  less  than  one-half  of  the 
thickness  of  the  pipe  must  not  be  over  8  inches  long.  Two  or 
more  cause  rejection. 

A  transverse  fire  crack  must  not  be  longer  than  one-sixth  of 
the  circumference  or  more  than  one-third  of  the  thickness  in 
depth.  Two  or  more  cause  rejection. 

No  fire  cracks  shall  be  over  one-eighth  of  an  inch  wide  at 
widest  point. 

No  combinations  of  above  limitations  allowed  except  by  special 
consent. 

Any  pipe  or  special  cracked  through  whole  thickness  from  any 
other  cause  than  burning  rejected.  This  refers  to  transporta- 
tion, cooling,  frost,  etc. 

Irregular  lumps  or  unbroken  blisters  on  interior  surface  suffi- 
cient to  appreciably  retard  flow  cause  rejection. 

Broken  blisters  or  flakes  must  not  exceed  in  thickness  one- 
sixth  of  the  thickness  of  the  pipe  or  in  greatest  diameter 
one-twelfth  of  the  circumference  of  the  pipe. 

Any  broken  blister  or  flake  so  placed  that  proper  fitting  of 
pipe  cannot  bring  it  on  top  will  cause  rejection. 


SEWER  PIPE  379 

The  same  applies  to  broken  blisters  on  outside. 

Any  pipe  showing  in  any  manner  a  want  of  thorough  vitri- 
fication or  fusion  or  use  of  improper  materials  or  methods  shall 
cause  rejection. 

All  pipe  supposed  to  be  straight  shall  not  show  any  material 
deviation. 

No  piece  broken  out  of  rim  of  either  hub  or  socket  of  pipe 
shall  be  greater  than  one-tenth  of  the  circumference  of  the 
pipe.  And  any  break,  even  within  limits,  shall  cause  rejection 
if  pipe  cannot  be  fitted  so  as  to  bring  break  at  top. 

A.  Mars  ton  1  points  out  that  the  standard  tests  of  drain  tile 
and  sewer  pipe  should  develop  two  cardinal  qualities:  (a)  The 
bearing  strength  of  the  pipe  under  approximate  conditions  and 
for  which  he  proposes  a  direct  bearing-strength  test,  (b)  The 
quality  of  the  material  in  the  shell  of  the  pipe  to  resist  disinte- 
gration, which  he  proposes  to  determine  by: 

1.  The  modulus  of  rupture  of  the  material,   calculated  from 
the  data  of  the  bearing-strength  test,  to  show  the  strength  of 
the  material. 

2.  An  absorption  test  of  the  material  to  show  its  resistance 
and  the  penetration  and  action  of  destructive  agencies. 

The  need  of  standard  tests  is  shown  by  the  fact  that  in  many 
cases  large  pipe  are  found  to  be  cracked  when  inspected  in 
building  sewers  and  drains,  and  that  this  cracking  is  sometimes 
caused  by  comparatively  shallow  depths  of  ditch  filling. 

As  a  result  of  numerous  experiments  in  Iowa,  the  Iowa  En- 
gineering Experiment  Station  has  devised  the  following  speci- 
fications for  standard  tests: 

Iowa  Standard  Specifications  for  Drain  Tile  and  Sewer  Pipe. 
Absorption  Tests,  i.  Specimens.  The  specimens  shall  be  each 
approximately  three  inches  square,  and  shall  extend  the  full 
thickness  of  the  pipe  wall,  with  the  outer  skins  unbroken. 

2.  Number  of  Test  Specimens.  Five  individual  tests  shall 
constitute  a  standard  test,  the  average  of  the  five  and  the 
result  for  each  specimen  being  given  in  the  report  of  the  test. 

1  Proceedings  American  Society  for  Testing  Materials,  Vol.  XI,  p.  833;  see 
also  " Municipal  Engineering,"  Vol.  30,  p.  288,  and  Vol.  34,  p.  294. 


380  BUILDING  STONES  AND  CLAY-PRODUCTS 

3.  Drying  Specimens.     Each  specimen  shall  be  dried  in  an 
oven,  or  by  other  application  of  artificial  heat,  until  it  ceases  to 
lose  further  appreciable  amounts  of  moisture  when  repeatedly 
weighed. 

4.  Brushing  Specimens.    All  surfaces  of  the  specimens  shall 
be  brushed  with  a  stiff  brush  before  weighing  the  first  time. 

5.  Weighing.     The  specimens  shall  be  weighed  immediately 
before  immersion,  on  a  balance  or  scales  capable  of  accurately 
indicating  the  weight  to  within  one-tenth  of  one  per  cent. 

6.  Water  for  Standard   Test.     The  water   employed  in   the 
standard  absorption  test  shall  be  pure  soft  water,  at  the  air 
temperature  of  a  room  which  is  artificially  heated  in  cold  seasons 
of  the  year. 

7.  Immersion  of  Specimens.     The  specimens  shall  be  com- 
pletely immersed  in  water  for  a  period  of  24  hours. 

8.  Re-weighing.     Immediately  upon  being  removed  from  the 
water,  the  specimens  shall  be  dried  by  pressing  against  them  a 
soft  cloth  or  a  piece  of  blotting  paper.     There  shall  be  no  rub- 
bing or  brushing  of  the  specimen.     The  re-weighing  shall  be 
done  with  a  balance  or  scales  capable  of  accurately  indicating 
the  weight  to  within  one- tenth  of  one  per  cent. 

9.  Calculation   of  Result.       The   result   of    each   absorption 
test  shall  be  calculated  by  taking  the  difference  between  the 
initial  dry  weight  and  final  weight,  and  dividing  the  remainder 
by  the  initial  dry  weight. 

Bearing  Strength,  i.  Specimens.  The  specimens  shall  be 
unbroken,  full-sized  samples  of  the  pipe  to  be  tested.  They 
shall  be  carefully  selected  so  as  to  represent  fairly  the  quality  of 
the  pipe. 

2.  Number  of  Specimens.     Five  individual  tests  shall  con- 
stitute a  standard  test,  the  average  of  the  five  and  the  result 
for  each  specimen  being  given  in  the  report  of  the  test. 

3.  Drying.     The  specimens  shall  be  dried  by  keeping  them  in 
a  warm,  dry  room  for  a  period  of  at  least  2  days  prior  to  the 
test. 

4.  Weighing.     Each  dried  specimen  shall  be  weighed  on  reli- 
able scales  just  prior  to  the  test. 

5.  Bedding  of  Specimen  for   Test.    Each  specimen  shall  be 
accurately  marked,   with  pencil  or  crayon  lines,   in   quarters, 
prior  to  the  test.     Specimens  shall  be  carefully  bedded  above 
and  below  in  sand  for  the  one-fourth  circumference  of  the  pipe, 
measured  on  the  middle  line  of  the  tile  wall.     The  depth  of 
bedding  above  and  below  the  tile  at  the  thinnest  point  shall  be 


SEWER  PIPE  381 

equal  to  one-fourth  the  diameter  of  the  pipe,  measured  between 
the  middle  lines  of  the  tile  walls. 

6.  Top  Bearing.     The  top-bearing  frame  shall  not  be  allowed 
to  come  in  contact  with  the  tile  or  the  test  load.     The  upper 
surface  of  the  sand  in  the  top  bearing  shall  be  carefully  struck 
level  with  a  straight  edge,  and  shall  be  carefully  covered  with 
a  heavy  rigid  top  bearing,  with  lower  surface  a  true  plane  made 
of  heavy  timber  or  other  rigid  material  capable  of  uniformly 
distributing   the   test   load   without   any   appreciable   bending. 
The  test  load  shall  be  applied  at  the  exact  center  of  this  top 
bearing  in  such  a  way,  either  by  the  use  of  a  spherical  bearing 
or  by  the  use  of  two  rollers  at  right  angles,  as  to  leave  the  bear- 
ing free  to  move  in  both  directions.     In  case  the  test  is  made 
without  the  use  of  a  machine  and  by  piling  on  weight,   the 
weight  may  be  piled  directly  on  a  platform  resting  on  the  top 
bearing,  provided,  however,  that  the  weight  does  not  touch  the 
top  frame  holding  the  sand,  and  provided,  further,   that  the 
weight  is  piled  in  such  a  way  as  to  insure  uniform  distribution 
of  the  load  over  the  top  surface  of  the  sand. 

7.  Frames  for  Top  and  Bottom  Bearings.  —  The   frames  for 
the  top  and  bottom  bearings  shall  be  composed  of  timbers  so 
heavy  as  to  avoid  any  appreciable  bending  by  the  side  pressure 
of  the  sand.     The  frames   shall  be  dressed  on   their  interior 
surfaces.     No  frame  shall  come  in  contact  with  the  tile  during 
the  test.     A  strip  of  soft  cloth  may  be  attached  to  the  inside 
of  the  upper  frame  on  each  side  along  the  lower  edge,  to  pre- 
vent the  escape  of  sand  between  the  frame  and  tile. 

8.  Sand  in  Bearings.     The  sand  used  for  bedding  the  tile  at 
the  top  and  bottom  shall  be  washed  sand  which  has  passed  a 
No.  8  screen.     It  shall  be  dried  by  keeping  it  spread  out  thin 
in  a  warm,  dry  room. 

9.  Application  of  Load.     The  test  load  shall  be  applied  grad- 
ually and  without  shock  or  disturbance  of  the  tile.     The  appli- 
cation of  the  load  shall  be  carried  on  continuously,  and  the  tile 
shall  not  be  allowed  to  stand  any  considerable  length  of  time 
under  a  load  ^smaller  than  the  breaking  load. 

10.  Calculation   of  the   Bearinr   Load.     The   total  breaking 
load  shall  be  taken  as  equal  to  tl     total  top  load,  including  the 
weight  of  top  frame,  sand  for  top  bearing,  top  bearing  timbers, 
etc.,  plus  five-eighths  the  weight  of  the  pipe.     This  total  load 
shall  be  divided  by  the  length  of  the  pipe  in  feet  so  as  to  give 
the  bearing  strength  per  linear  foot  of  pipe. 

Computing  the  Modulus  of  Rupture.     The  modulus  of  rupture 


382 


BUILDING   STONES  AND   CLAY-PRODUCTS 


for  drain  tile  and  sewer  pipe  shall  be  computed  from  the  results 
of  the  standard  test  for  bearing  strength,  according  to  the 
following  rule: 

Divide  the  bearing  strength  per  linear  foot  by  twelve,  mul- 
tiply the  quotient  by  the  radius  of  the  middle  line  of  tile  wall 
expressed  in  inches,  and  divide  this  product  by  the  square  of  the 
minimum  thickness  of  the  tile  wall  at  top  or  bottom,  also  ex- 
pressed in  inches.  This  quotient  will  be  the  modulus  of  rup- 
ture of  the  pipe,  expressed  in  pounds  per  square  inch. 

The  formulas  on  which  the  above  specifications  are  based 
are  derived  in  the  usual  manner  for  flexible  rings  subjected 
to  uniform  vertical  loads,  over  90°  of  the  circumference  above 
and  the  same  distance  below.  The  mathematical  details  of 
the  derivation  will  not  be  given.  Use  is  made  in  work  of  both 
the  static  and  the  elastic  equations  of  equilibriums. 

BRIEF    SUMMARY    OF    ABSORPTION    TESTS    OF    DRAIN    TILE 

AND   SEWER  PIPE.     IOWA   STANDARD  METHOD. 

Tests  of  Clay  Drain  Tile. 


No.  of  tests. 

No.  of 
kinds. 

Diameter  of 
tile, 
ins. 

Per  cent  of  absorption. 

Minimum. 

Maximum. 

Average. 

4 
30 

2 

42 

5 
4 
5 

I 
3 

2 
2 

I 
I 
I 

6 
8 

12 

18 
28 
30 

15-0 
2  .  6-4  .  0 

18-5 
7-3-8-3 

16.3 
4.8-6.1 
3.6-19.0 
5-0-5-8 

5-5 
5-4 
4-3 

2-4-3-Q 
4.1 
4.8 
3-4 

7-6 
8.8 
6.1 

5-2 

Other  Proposed  Standard  Tests.  A  number  of  other  meth- 
ods of  making  bearing-strength  tests  of  drain  tile  and  sewer 
pipe  have  been  advocated  or  used.  Together  with  the  above 
method,  they  may  be  enumerated  as  follows: 

1.  Completely   surrounding   the  pipe  with  sand  in  a  very 
strong  box.     The  author  understands  that  this  method  was  in 
use  for  a  time  in  Brooklyn.    It  has  been  strongly  advocated  by 
Blackmer  and  Post  of  St.  Louis,  in  recent  correspondence,  and 
they  have  made  a  new  design  for  the  enclosing  box  and  the 
bearings. 

2.  Bedding  the  pipe  on  sand  at  the  bottom,  while  applying 
the  top  load   to  a  narrow  bearing  strip.     The  author  would 
designate  this  the  Brooklyn  Method,  as  it  is  in  regular  use  by 
the  sewerage  engineers  of  that  city. 


SEWER  PIPE 


383 


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384 


BUILDING  STONES  AND   CLAY-PRODUCTS 


3.  The   Iowa   Standard   Method,   already  described   herein, 
beds  the  pipe  in  sand  for  90°  at  the  top,  and  the  same  amount 
at  the  bottom. 

4.  In  the  so-called  Three  Point  Method,  the  pressure  is  ap- 
plied along  a  single  narrow  bearing  strip  at  the  top,  while  the 
pipe  is  supported  at  the  bottom  on  two  similar  bearing  strips, 
placed  parallel,   a  few  inches  apart.     This  method  has  been 
developed  by  Mr.  C.  W.  Boynton,  of  Chicago,  and  in  the  lab- 
oratory of  Professor  A.  N.  Talbot,  of  the  University  of  Illinois. 
The  Iowa  Engineering  Experiment  Station  has  made  quite  a 
number  of  comparative  tests  with  this  method. 

5.  In  the  method  of  Concentrated  Loadings,  the  top  load 
would  be  applied  to  a  narrow  bearing  strip  as  in  Methods  2 
and  4,  and  the  bottom  of  the  pipe  would  be  supported  on  a 
similar  bearing  strip. 

Miscellaneous  Tests.  The  following  tests  of  sewer  pipe  are 
given  in  Ogden's  book  on  Sewer  Construction.  Tests  were 
made  by  J.  H.  Shedd,  1879,  on  pipes  half  bedded  in  sand. 
Results  show  crushing  strength  in  pounds  per  linear  foot. 


No.  of 

kinds. 

Minimum. 

Maximum. 

Average. 

i2-inch  pipes  

4 

I4<6 

176^ 

1601 

i5-inch  pipes  

4 

1261 

176^ 

14^2 

i8-inch  pipes 

•2 

14.64 

104-2 

1670 

A  set  of  hydrostatic  tests  were  made  in  1890  by  M.  A.  Howe, 
by  having  the  end  of  the  pipe  closed  and  the  water  pumped  in 
until  the  pipe  broke.  The  average  tensile  strength  of  the  ma- 
terial for  the  different  sizes  was  as  follows: 

4-inch 517  pounds 

6-inch 678  pounds 

8-inch 552  pounds 

lo-inch 702  pounds 

12-inch 592  pounds 

i8-inch 529  pounds 

2i-inch 617  pounds 

24-inch 856  pounds 

A  drop  test  showed  that  the  sewer  pipe  has  strength  enough 
to  sustain  ordinary  blows,  but  that,  where  successive  blows  are 
to  be  expected,  sufficient  covering  is  to  be  provided. 


SEWER  PIPE  385 

In  a  concentrated-load  test,  an  average  pipe  stood  2000  pounds 
at  the  center,  with  supports  16  inches  apart. 

The  uniform-load  test  showed  that  the  larger  sizes  stood  a 
little  over  2000  pounds  per  linear  foot  of  pipe,  and  the  smaller 
sizes  up  to  8000  pounds. 

Mr.  Barbour,  city  engineer  at  Brockton,  Mass.,  recommended, 
as  a  result  of  tests  made  by  him,  that  pipe  be  required  to  have 
a  breaking  load  of  3000  pounds  per  linear  foot  for  a  standard, 
and  4500  pounds  per  linear  foot  for  double-strength  pipe,  the 
thickness  to  vary  with  the  diameter  to  give  this  strength. 

Other  tests  made  in  1894  by  the  city  engineer  of  Providence, 
R.  I.,  showed  the  following  variation  in  the  crushing  strength  per 
linear  foot: 

8-inch:  Minimum,  757  pounds;  Maximum,  2498  pounds 
12-inch:  Minimum,  924  pounds;  Maximum,  2816  pounds 
15-inch:  Minimum,  1063  pounds;  Maximum,  2666  pounds 
i8-inch:  Minimum,  1305  pounds;  Maximum,  2401  pounds 

These  were  simply  to  indicate  the  danger  of  pipes  breaking 
even  if  loaded  approximately  to  what  the  average  pipe  will  bear. 

Other  Hollow  Shapes.  Among  the  other  hollow  shapes  often 
made  at  sewer-pipe  works  are  fire-clay  stove-pipe  fittings,  such 
as  thimbles,  flue  tops,  and  flue  linings.  The  latter  are  made 
either  with  circular  section  or  rectangular  with  round  corners, 
and  usually  in  two-foot  lengths. 

The  weights  of  flue  linings  in  two-foot  lengths  are  about  as 
follows: 

4^  X  8£  inches  outside 14  pounds 

6     X  12  inches  outside 22  pounds 

8£  X  8|  inches  outside 18  pounds 

85  X  13  inches  outside 28  pounds 

12  X  16  inches  outside 45  pounds 

13  X  13  inches  outside 38  pounds 

13  X  18  inches  outside 57  pounds 

14  X  16  inches  outside 50  pounds 

18  X  18  inches  outside 75  pounds 

Vitrified  round  drain  tile  are  now  produced  in  large  quantities 
at  some  sewer-pipe  works.  They  are  either  glazed  or  unglazed. 
The  following  figures  are  given  by  one  factory: 


386 


BUILDING  STONES  AND   CLAY-PRODUCTS 


Diameter, 
inches. 

Weight  per  loot, 
pounds. 

No.  of  feet  drain 
tile  in  carload 
(3000  pounds). 

2 

3* 

2| 

4 

7500 

3 

5 

6OOO 

4 

1\ 

4OOO 

5 

10 

3000 

6 

13 

2310 

8 

20 

1500 

10 

30 

IOOO 

12 

40 

750 

Sewer  Blocks.  These  are  hollow,  segmental  blocks,  which  are 
used  in  the  construction  of  large  diameter  sewers,  ranging,  say, 
from  36  inches  to  108  inches.  Like  the  sewer  pipe  they  are  or 
should  be  vitrified,  and  are  also  salt  glazed. 


1     Type  B      ; 


5§§§§ 

^^^^^^^^^^^^^^^5 

Type  B 

a, 

k-lJXr> 

Fig.  20.  —  Sections  of  sewer  blocks.     (American  Sewer  Pipe  Company.) 


The  following  data  are  taken  from  the  catalogue  of  the  Ameri- 
can Sewer  Pipe  Company. 


SEWER   PIPE 


387 


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388  BUILDING  STONES  AND   CLAY-PRODUCTS 

SANITARY  WARE. 
Sanitary  ware  is  divided  into  two  classes,  viz.: 

(1)  Vitreous  Ware,  from  which  are  made  water-closets,  tanks, 
high  and  low  lavatories  and  drinking  fountains.     This  class  of 
ware  is  made  in  two  fires,  viz.,  biscuit  and  glost  fire. 

(2)  Solid  Porcelain,  so  called  in  the  trade,  the  body  being 
made  of  fire  clay  and  fire-clay  grog,  which  is  covered  with  a 
white  vitreous  lining,  the  latter  in  turn  being  covered  with  a 
hard,  clear,  feldspathic  glaze.     The  lining  and  glaze  are  applied 
to  the  green  ware,  and  the  whole  burned  in  one  fire  in  a  rec- 
tangular muffle  kiln.     In  this  type  are  made  solid  porcelain  bath- 
tubs, urinals,  stalls,  laundry  trays,  kitchen  and  pantry  sinks, 
slop  sinks,  lavatories,  etc.     It  is  sold  as  A,  B,  C  grades. 

When  the  white  lining  is  omitted  a  buff-colored  ware  results, 
which  is  of  a  cheaper  grade  and  known  as  Continental  ware. 

Raw  Materials.  The  body  of  vitreous  ware  consists  of  several 
grades  of  kaolin,  ball  clay,  whiting,  flint  and  feldspar.  The 
body  of  solid  porcelain  ware  is  made  of  a  mixture  of  several 
grades  of  fire  clay  and  fire-clay  grog.  The  glaze  of  the  former 
consists  of  feldspar,  Cornwall  stone,1  whiting,  zinc  oxide,  white 
lead,  kaolin,  flint  and  boric  acid,  while  the  glaze  of  the  solid 
porcelain  ware  is  similar  but  contains  no  lead  and  tin  oxide. 

Manufacture.  Sanitary  ware  is  formed  by  hand  in  plaster 
molds.  Great  care  has  to  be  taken  to  mix  the  clays  properly 
and  to  dry  the  ware  slowly  after  it  has  been  formed.  Vitreous 
ware  is  first  burned  to  the  "  biscuit  "  condition,  then  glazed  and 
fired  again  in  the  glost  kiln,  but  at  a  lower  temperature,  in  order 
to  fuse  the  glaze. 

The  solid  porcelain  has  the  glaze  applied  to  the  green  ware 
and  the  whole  fired  in  one  operation. 

Properties  of  Sanitary  Ware.  The  body  of  both  kinds  of 
sanitary  ware  should  be  steel  hard,  and  the  vitreous  ware  is 
non-absorbent.  They  should  not  discolor,  and  the  glaze  should 
be  smooth  and  free  from  cracks. 

The  visible  defects  are  chiefly  in  the  glaze,  which  may  dunt, 
fire  crack,  or  craze.  It  may  also  shrink  away  from  the  edges  of 

1  A  partially  decayed  granite. 


SANITARY    WARE  389 

the  ware.  The  glaze  may  also  show  green  or  brown  spots.  If 
underfired  it  is  dull,  if  overfired  it  blisters. 

Proper  shrinkage  of  the  ware  in  burning  is  highly  important. 

The  disadvantages  claimed  for  marble,  slate  and  soaps  tone, 
as  compared  with  clay  ware,  are  that  they  lack  uniformity  of 
color,  are  not  non-absorbent,  and  in  the  case  of  marble  at  least 
are  affected  by  acid  waters.  Glass  is  claimed  to  be  more  brittle 
than  the  clay  ware.  Enameled  iron  ware  is  said  by  some  to  be 
less  durable. 

Sanitary  ware  made  of  burned  clay  is  now  widely  used  in  the 
United  States.  It  has  grown  tremendously  in  favor  in  recent 
years  and  has  also  improved  greatly  in  quality.  Much  was 
formerly  imported  from  Europe. 

An  objection  urged  by  some  is  the  higher  cost  and  great  weight. 
A  finished  bathtub  may  commonly  weigh  from  500  to  800  pounds, 
according  to  size  and  shape. 


GLOSSARY. 

Adobe.     A  sandy,  often  calcareous  clay,  much  used  in  warm  climates  for  making 

sunbaked  (adobe)  brick. 

Air  shrinkage.     The  decrease  in  volume  which  a  clay  undergoes  in  drying. 
Air  brick.     A  hollow  or  pierced  brick  built  into  a  wall  to  allow  the  passage  of  the  air. 
Alabaster.     A  white,  massive  variety  of  gypsum. 
Amphibole.     A  group  name  including  a  number  of  mineral  species,  which  are 

essentially  silicates  of  alumina,  magnesia,  lime  and  iron.     They  are  found  in 

both  igneous  and  metamorphic  rocks.     Hornblende  is  the  commonest  species. 
Anticline.     An  arch-like  fold. 
Apatite.     A  mineral  occurring  in  many  granites,  but  usually  in  small  quantities. 

It  is  a  phosphate  of  lime  and  has  a  hardness  of  5. 
Aplite.     A  line-grained  granite,  consisting  normally  of  quartz  and  feldspar,  and 

usually  occurring  in  dikes. 
Aragonite.     A  mineral  having  the  same  composition  as  calcite  (calcium  carbonate) 

but  differing  from  it  in  crystalline  form. 
Arch  brick.     Commonly  applied  to  those  brick  taken  from  the  arches  of  a  kiln. 

They  are  usually  overburned. 

Argillaceous.     A  common  term  applied  to  rocks  containing  clayey  matter. 
Arkose.     A  variety  of  sandstone  containing  much  feldspar. 
Ashlar  brick.     A  term  often  applied  to  certain  brick  whose  one  edge  is  rough 

chiseled  to  resemble  rock -faced  stone. 

Ball  clay.      A  plastic  white-burning  clay  used  as  a  bond  in  china  ware. 
Basalt.     An  igneous  rock  of  volcanic  character,  composed  chiefly  of  pyroxene  and 

plagioclase  feldspar.     It  is  usually  fine-grained  and    black,   is  common  in 

the  northwestern  states,  but  is  little  used  for  building  purposes.     See  Trap. 
Bastard  granite.     Many  quarrymen  apply  this  term  to  gneissic  granites. 
Bate.     See  False  cleavage. 
Bedding.     See  Stratification. 
Biotite.     A  mica,  essentially  a  silicate  of  aluminum,  magnesia  and  iron,  of  black 

or  dark  green  color. 
Black  coring.     The  development  of  black  or  bluish  black  cores  in  bricks,  due  to 

improper  burning. 
Blind  seams.     Incipient  joints. 
Bluestone.     An  indefinite  term  commonly  applied  to  sandstones  of  a  bluish  gray 

color.     In  Maryland  it  is  used  for  a  gray  gneiss,  and  in  the  District  of  Columbia 

for  a  mica  schist.     The  well-known  bluestone  of  eastern  New  York  is  used 

for  flagging. 
Book  tiles.     Flat,  hollow  shapes,  having  two  segmental  edges  and  resembling  a 

book  in  section. 
Boulder  quarry.     A  quarry  in  which  the  joints  are  numerous  and  irregular,  so  that 

the  stone  is  naturally  broken  up  into  comparatively  small  blocks. 

390 


GLOSSARY  391 

Breccia.     A  rock  composed  of  angular  fragments,  usually  cemented  together. 

Brick  clay.     Any  clay  that  can  be  used  for  brick  manufacture. 

Brownstone.     A  term  properly  referring  to  a  brown  sandstone,  but  now  very  loosely 

used. 

Calcareous.     Containing  lime,  as  a  calcareous  sandstone  or  calcareous  day. 
Calcareous  tufa.     A  porous  mass  of  lime  carbonate,  deposited  around  the  mouth  of 

springs,  as  in  swamps,  or  on  rock  ledges.     It  often  forms  a  coating  on  plants. 
Colette.     A  mineral  species  composed  of  lime  carbonate.     The  chief  constituent  of 

many  limestones. 

Calc-sinter.     Same  as  Calcareous  tufa. 
Calico  marble.     A  name  applied  to  the  limestone  conglomerate  quarried    near 

Point  of  Rocks,  Maryland. 
Cellular.     Containing  cells,  vesicles  or  cavities.     A  term  most  often  applied  to 

lavas. 
Chalk.     A  soft  limestone,  of  earthy  texture  and  usually  white  color.     Not  of  much 

use  as  a  building  stone. 
Chert.     A  non-crystalline  variety  of  quartz,  often  occurring  as   concretions  in 

limestones.     It  is  either  dark  or  light  in  color  and  has  a  conchoidal  or 

rounded  fracture. 
China  clay.      See  Kaolin. 
Chlorite.     A  group  name  for  certain  micaceous  minerals,  usually  of  greenish  color, 

and  being  silicates  containing  alumina,  iron  and  magnesia.     Common  in 

metamorphic  rocks.     Hardness,  2-2.7. 

Cipolino  marble.     A  white  marble,  having  veins  of  greenish  mica. 
Clay.     An  earthy  rock,  having  plasticity  when  wet,  and  hardening  when  burned. 
Clay  holes.     Cavities  in  stones  often  filled  with  sandy  or  clayey  matter,  which 

usually  falls  out  on  exposure  to  the  weather. 
Cleavage.     The  property  which  some  minerals  and  metamorphic  rocks  have  of 

splitting  readily  in  certain  definite  directions,  which,  in  the  case  of  minerals, 

are  at  a  constant  angle  with  themselves  and  with  respect  to  the  crystal  form. 
Clinker  brick.     A  very  hard-burned  brick. 
Conchoidal  fracture.     This  applies  to  a  curved  break,  resembling  the  curve  of  a 

clamshell.     Dense  rocks  and  some  minerals  often  break  in  this  way. 
Concretionary.     Made  up  of  concretions. 

Concretions.     More  or  less  rounded  bodies  of  foreign  matter  found  in  some  sedi- 
mentary rocks.     They  are  often  chert  in  limestone,  and  lime  carbonate  or 

iron  carbonate  in  some  clays  and  shales. 
Conglomerate.     A  sedimentary  rock  made  up  chiefly  of  rounded  fragments.     Also 

called  pudding  stone. 
Continuous  kiln.     One  in  which  the  waste  heat  from  the  cooling  or  hot  chambers 

of  brick  is  used  to  heat  up  the  wares  in  other  compartments  still  to  be  burned. 
Coquina.     A  limestone  made  up  of  loosely  cemented  shell  fragments. 
Coral  limestone.     One  composed  of  coral  fragments.     Such  a  rock  is  much  used  in 

the  Bermuda  Islands. 

Cresting.    Trimming  used  on  the  ridge  of  tiled  roofs.     Same  as  Hip  rolls. 
Crocus.     A  name  applied  to  gneiss  or  other  rock  in  contact  with  granite,  in  some 

quarries. 
Cryptocrystalline.     Finely  crystalline.     A  term  applied  to  igneous  rocks. 


3Q2  BUILDING   STONES  AND   CLAY-PRODUCTS 

Crystalline  rocks.     A  term  applied  to  those  rocks  composed  of  interlocking  crystal- 
line mineral  grains,  which  have  crystallized  from  fusion  or  solution. 
Cut-off.     The  direction  along  which  granite  must  be  channeled  because  it  will  not 

split. 
Deck  molding.     Trimming  made  to  match  cresting  or  ridging,  on  clay-tiled  roofs, 

and  used  for  the  purpose  of  covering  the  planes  of  a  roof  which  has  a  flat  deck. 
Decomposition.     A  term  sometimes  used  to  refer  to  the  chemical  breaking  down  of 

a  rock  on  weathering. 
Diabase.     An  igneous  rock  of  ophitic  (q.  v.)  texture,  usually  fine  to  medium  grained, 

and  consisting  chiefly  of  pyroxene  and  plagioclase  feldspar. 

Dike.     Igneous  rock  which  has  been  forced  into  a  fissure  which  is  narrow  as  com- 
pared with  its  other  dimensions.     It  may  vary  from  a  few  inches  to  a  number 

of  feet  in  width. 

Dimension  stone.     Stone  that  is  quarried  or  cut  of  required  dimensions. 
Diorite.     An  igneous  rock,  usually  of  granitic  texture,  either  fine  or  coarse  grained, 

and  composed  essentially  of  plagioclase,  feldspar  and  hornblende. 
Diorite  porphyry.     A  rock  of  porphyritic  texture,  but  of  the  same  mineral  composi- 
tion as  diorite. 

Dip.     The  slope  of  strata,  or  the  angle  which  they  make  with  a  horizontal  plane. 
Disintegration.     A  term  often  applied  to  the  natural  mechanical  breaking  down  of 

a  rock  on  weathering. 
Dolomite.     A  mineral  which  is  a  double  carbonate  of  calcium  (lime)  and  magnesium. 

Also  a  rock  consisting  chiefly  of  the  mineral  dolomite. 
Down-draft  kiln.     One  in  which  the  heat  enters  the  kiln  chamber  from  the  top  and 

passes  down  through  the  ware. 
Dries  or  Dry.     A  seam  in  the  rock,  which  is  usually  invisible  in  the  freshly  quarried 

material,  but  which  may  open  up  in  cutting  or  on  exposure  to  the  weather. 
Dryer  white.     A  white  scum  which  forms  on  brick  during  drying. 
Dry  pan.     A  circular  revolving  pan  with  perforated  bottom,  in  which  two  large 

rollers  revolve  by  friction  against  the  pan  floor.     It  is  used  for  grinding  dry 

clays. 
Dry-press  process.     A  method  of  forming  clay  wares  by  using  slightly  moistened 

clay  in  pulverized  form  and  pressing  it  into  steel  dies. 

Dust  pressed.     Same  as  dry  pressed.     Usually  applied  to  manufacture  of  wall  tile. 
Eave  tile  or  Starters.     These  are  roofing  tile,  closed  underneath  at  the  lower  end. 

They  are  placed  at  the  eave  line. 
Enameled  brick.     Brick  which  are  coated  on  one  or  two  surfaces  with  a  white  or 

colored  enamel. 
Encaustic  tile.     Floor  tile  having  a  surface  pattern  of  one  type  of  clay  and  backing 

of  a  different  one. 
End  bands.     Half  tile,  made  by  cutting  whole  tile  longitudinally,  and  used  where 

the  roof  butts  against  a  vertical  surface. 
Extrusive.    A  term  applied  to  those  igneous  rocks  which  have  cooled  after  reaching 

the  surface. 

False  cleavage.    Very  fine  plications,  seen  on  the  cleavage  surfaces  of  slates. 
Fault.    A  slipping  of  rock  masses  along  a  fracture.    Faults  may  occur  in  any  kind 

of  rock. 


GLOSSARY  393 

Felsite.     A  compact,  fine-grained,  light-colored  volcanic  rock  of  the  same  mineral 

composition  as  rhyolite  or  trachyte,  whose  mineral  grains  are  too  small  to 

be  recognized  by  the  naked  eye. 
Feldspar.     A  name  applied  to  a  group  of  minerals  having  slightly  different  physical 

properties,  and  which  are  silicates  of  aluminum,  with  potassium,  sodium  and 

calcium.     Thus  orthoclase  is  a  silicate  of  aluminum  and  potassium,  while 

plagioclase  is  a  silicate  of  aluminum  with  calcium  or  sodium  or  both.     They 

have  a  pronounced  cleavage  and  a  hardness  of  6.     Color  generally  pink  or 

whice.     Very  abundant  in  igneous  and  some  metamorphic  rocks  and  rare  in 

sandstones. 

Ferruginous.     Containing  iron  oxide. 
Ferro-magnesian.     A  term  often  applied  to  the  dark  silicates  found  in  igneous 

rocks,  and  which  contain  both  iron  oxide  and  magnesia. 
Finial.     Ornamental  pieces  of  burned  clay  used  for  finishing  off  the  joining  of  the 

ridge  line  with  the  hips,  ridge  line  at  gables,  or  top  of  a  tower. 
Fire  brick.     One  made  of  fire  clay,  and  capable  of  standing  a  high  degree  of  heat 

(not  less  than  2700°  F.). 

Fire  clay.     One  capable  of  standing  a  high  temperature. 
Fireproofing.     A  general  name  applied  to  those  forms  used  in  the  construction  of 

floor  arches,  partitions,  etc.,  for  fireproof  buildings. 
Fire  shrinkage.     The  decrease  in  volume  which  a  clay  shows  in  burning. 
Fissility.     The  tendency  which  some  rocks  show  of  separating  into  thin  laminae. 
Flagstone.     A  term  applied  especially  to  sandstones  which  split  naturally  into  thin 

slabs  suitable  for  flagging. 
Flashed  brick.     This  term  includes  those  brick  which  have  had  their  edges  darkened 

by  special  treatment  in  firing. 

Flint.     This  is  practically  the  same  as  chert,  which  see. 
Flue  linings.     Pipe  of  cylindrical  or  rectangular  cross  section  used  for  lining  flues. 

Usually  made  of  a  low-grade  fire  clay. 
Flue  tops.     A  form  of  burned  clay  ware,  often  of  ornamental  character,  placed  on 

the  top  of  chimney  flues. 
Flow  structure.     A  streaked  or  banded  structure  shown  by  many  igneous  rocks 

and  caused  by  a  flowing  movement  of  the  rock  while  soft. 
Foliated.     See  Schistose. 

Forest  marble.     An  argillaceous  limestone  in  which  the  coloring  matter  is  so  dis- 
tributed as  to  resemble  forests. 
Freestone.     A  stone  that  works  easily  or  freely  in  any  direction.     It  is  applied 

especially  to  sandstones  and  limestones. 
Frog.     See  Key. 
Furring  brick.     Hollow  brick  for  lining  or  furring  the  inside  of  a  wall.     Usually  of 

common  brick  size,  with  surface  grooved  to  take  plaster. 
Gabbro.     A  granular  igneous  rock,  consisting  chiefly  of  pyroxene  and  feldspar. 

The  former  may  predominate  to  such  an  extent  as  to  give  the  stone  a  black 

color. 

Gable  rake  tile.     The  full-flanged  tile  used  at  the  verge  of  open  gables. 
Garnet.    A  mineral  which  is  a  silicate  of  alumina,  lime,  iron  or  magnesia.     Its 

hardness  is  6-7,  color  often  red,  and  grains  frequently  rounded. 


394  BUILDING  STONES  AND  CLAY-PRODUCTS 

Gneiss.     A  metamorphic  rock,  having  the  minerals  arranged  in  more  or  less  massive 

bands  or  layers.     It  is  most  commonly  of  the  same  composition  as  granite 

and  might  then  be  called  a  granite  gneiss.     Other  types,  however,  are  known, 

as  syenite-gneiss,  diorite- gneiss,  etc. 

Gneissic.     Having  a  structure  resembling  that  of  gneiss  (q.  v.). 
Graduated  tile.     Roofing  tile  which  are  required  for  covering  curved  surfaces  such 

as  a  round  tower,  circular  bays  and  other  circular  roofs. 
Grain.     A  term  used  to  indicate  the  second  best  direction  of  splitting.     In  granite 

it  is  usually  at  right  angles  to  the  rift;  in  slates  it  forms  an  angle  to  the  cleavage. 

The  term  is  also  used  to  refer  to  the  texture  of  a  rock. 
Granite.     A  plutonic  igneous  rock,  usually  even  granular,  of  either  fine  or  coarse 

grain.     It  is  composed  essentially  of  quartz  and  orthoclase  feldspar,  and  one 

or  more  minerals  of  the  mica,  amphibole  or  pyroxene  series. 

Granite-porphyry.     A  rock  of  porphyritic  texture  and  of  the  same  mineral  composi- 
tion as  granite. 

Granitoid.     Having  a  texture  like  granite. 

Granodiorite.     A  diorite  (q.  v.),  carrying  a  considerable  percentage  of  quartz. 
Graywacke.     A  sandstone  of  compact  character,  composed  of  grains  of  quartz, 

feldspar  and  argillaceous  matter. 
Greenstone.   An  indefinite  term  often  applied  to  many  dark  igneous  rocks  of  a  green 

color,  the  latter  being  due  often  to  chlorite.     The  term  greenstone  is  applied 

to  gabbro  and  basalt,  diabase  and  diorite. 

Grit.     A  sharp,  gritty  sandstone,  especially  one  used  as  a  whetstone. 
Grog.     Ground  up  pieces  of  burned  clay  or  brick,  added  to  the  raw  clay  mixture 

for  the  purpose  of  decreasing  the  shrinkage  and  density  of  the  burned  ware. 
Hardway.     A  direction  of  splitting  at  right  angles  to  rift  and  grain.     Same  as 

Cut-off. 
Harvard  brick.     A  term  originally  applied  to   clear,  red,  common  brick,  which 

were  overburned,  and  especially  so  on  one  end  or  side,  so  that  these  harder 

burned  parts  were  bluish  black.     The  name  is  more  loosely  used  nowadays. 
Header.     A  brick  or  stone  laid  with  its  greatest  length  at  right  angles  to  the  surface 

of  the  wall. 
Heading.     A  term  sometimes  used  in  quarrying  to  apply  to  a  collection  of  close 

joints. 
Hematite.     A  mineral  which  chemically  consists  of  iron  oxide  (Fe2Os).     Its  powder 

is  red. 
Hip  and  ridge  angle.     A  piece  of  roofing  tile  required  where  a  hip  starts  from  a 

ridge. 
Hip-roll.     A  tile  used  for  covering  the  hips  on  roofs,  and  which  in  cross  section  may 

show  either  roll  or  an  angle. 

Hip  roll  starter.     A  closed  hip  piece  of  roofing  tile  used  at  the  lower  end  of  a  hip  roll. 
Hip  tile.     Tile  which  run  up  against  a  hip  stringer. 

Holocrystalline.     A  term  applied  to  igneous  rocks,  which  are  usually  crystalline. 
Hollow  blocks.    These  are  hollow  shapes,  larger  than  common  brick,  usually  of 

rectangular  form,  and  having  some  cross  webs.     Used  in  exterior  walls  and 

also  partitions. 
Hollow  brick.     Brick   molded   with   hollow  spaces   in  them.    They  are   usually 

strengthened  by  cross  webs. 


GLOSSARY  395 

Igneous  rock.    One  which  has  formed  by  the  cooling  of  a  molten  mass  of  rock. 

Interlocking  tile.  Roofing  tile  having  ridges  and  grooves  which  interlock  when  the 
tile  are  laid  on  the  roof. 

Intrusive  rocks.  A  term  applied  to  those  igneous  rocks  which  have  solidified  with- 
out reaching  the  surface.  Their  occurrence  on  the  surface  now  is  because  the 
rocks  which  were  above  them  have  been  worn  away. 

Iron  pyrite.     See  Pyrite. 

Joints.  Fractures,  often  steeply  inclined,  which  may  occur  in  any  kind  of  rock. 
They  are  usually  arranged  in  one  or  more  series,  those  of  the  same  series  being 
parallel.  Horizontal  joints  in  granites  develop  a  sheeted  structure. 

Kaolin.  A  white  residual  clay  (q.  v.)  used  in  the  manufacture  of  wall  tile,  china 
and  sanitary  ware. 

Key,  Frog  or  Panel.     A  rectangular  depression,  in  one  or  both  flat  sides  of  a  brick. 

Kiln  white.     A  scum  which  originates  in  the  burning  of  brick. 

Knots.  A  term  often  used  to  apply  to  bunches  or  segregations  of  dark  minerals 
found  in  granites  and  gneisses.  Sometimes  applied  to  concretions  found  in 
sedimentary  rock. 

Lava.  A  molten  rock,  especially  one  flowing  out  over  the  surface.  The  term  is 
also  applied  to  the  solidified  rock. 

Ledge.  This  term  is  usually  applied  to  one,  or  a  group  of  several  beds  occurring 
in  a  quarry.  Also  a  ridge  of  solid  rock  outcropping  at  the  surface. 

Lift.  The  name  sometimes  applied  to  joint  planes  which  are  approximately  hori- 
zontal. 

Limestone.  The  name  properly  belongs  to  rocks  composed  of  lime  carbonate. 
They  grade  into  dolomites  with  an  increase  of  magnesium  carbonate.  Inter- 
mediate types  are  spoken  of  as  magnesian  or  dolomitic  limestones.  Clay  and 
quartz  are  common  impurities. 

Limonite.  The  hydrous  iron  oxide  commonly  found  in  many  rocks.  It  is  usually 
of  brownish  color. 

Liver  rock.  Merrill  states  that  this  term  is  applied  to  a  variety  of  Ohio  sandstone 
which  breaks  or  cuts  readily  in  one  direction  or  another. 

Lustre.  The  natural  polish  or  reflection  shown  by  the  surface  of  some  minerals. 
Different  kinds  are  recognized,  such  as  vitreous,  pearly,  greasy,  silky,  etc. 

Magnetite.  The  magnetic  iron  oxide  (Fe3O4).  It  may  occur  in  the  darker  colored 
igneous  rocks  and  slate,  but  usually  in  microscopic  grains. 

Marble.  True  marbles  are  crystalline  limestones,  formed  by  the  metamorphism  of 
either  limestones  proper  or  dolomite.  In  the  trade  the  term  is  sometimes 
loosely  used  to  apply  to  any  limestone  that  will  take  a  polish. 

Matrix.  Also  called  ground  mass.  It  refers  to  the  general  body  of  the  rock,  which 
often  has  isolated  crystals  scattered  through  it. 

Matt  glaze.    A  dull  glaze  applied  to  some  burned  clay  products. 

Metamorphic  rocks.  Those  derived  from  igneous  or  sedimentary  rocks  through  the 
agency  of  heat,  pressure,  chemical  action,  or  all  three,  acting  on  them  when 
they  are  more  or  less  deeply  buried  in  the  earth's  crust. 

Mexican  tile.     A  term  sometimes  applied  to  roofing  tile  of  semicircular  cross  section. 

Mica.  A  group  name  of  minerals  which  are  silicates  of  alumina,  together  with 
potash,  lithia,  magnesia  and  iron.  They  show  a  perfect  cleavage  and  split 
easily  into  thin  elastic  plates.  See  Muscovite,  Biotite,  Phlogopite. 


396  BUILDING  STONES  AND  CLAY-PRODUCTS 

Micaceous  sandstone.     One  containing  numerous  scales  of  mica. 

Mission  tile.    A  name  sometimes  applied  to  roofing  tile  of  semicircular  cross 

section. 
Miter ed  tile.    Roofing  tile  that  are  cut  off  obliquely,  so  as  to  fit  in  upright  work, 

such  as  dormer  corners.     It  also  includes  pieces  flanged  at  right  angles  so  as 

to  cover  such  corners. 

Molded  brick.    A  term  sometimes  used  for  soft-mud  brick. 
Monolith.    A  single  piece  of  stone. 
Monzonite.    A  rock  of  intermediate  mineral  composition  between  a  diorite  and 

syenite. 

Norman  tile.     Brick  having  the  dimensions  12  by  2  j  to  2 1  by  4  inches. 
Obsidian.     A  volcanic  glass,  usually  of  acidic  character. 
Olivine.    The  common  species  is  a  silicate  of  magnesia,  often  of  green,  glassy 

character,  and  with  a  hardness  of  6-17.     It  is  a  constituent  chiefly  of  the 

darker  igneous  rocks  such  as  basalt,  diabase  and  gabbro. 

Onyx.    True  onyx  is  a  stone  resembling  agate,  made  up  of  layers  of  silica  of  dif- 
ferent colors.    The  ornamental  onyx  or  onyx  marble  is  a  carbonate  of  lime 

deposit,  often  colored  by  iron. 
Oolitic.    Made  up  of  very  small  rounded  concretions,  having  the  appearance  of 

fish  roe. 
Ophitic.     A  term  relating  to  texture,  consisting  of  interlacing  lath-shaped  crystals 

of  feldspar  whose  interspaces  are  chiefly  filled  by  pyroxene  of  later  growth. 
Orbicular  granite.     A  granite  containing  numerous  rounded  segregations  of  minerals, 

chiefly  dark  silicates. 
Ornamental  brick.    A  somewhat  broad  term  applied  to  front  brick  which  are  either 

of  some  form  other  than  that  of  a  rectangular  prism,  or  which  have  the 

surface  ornamented  with  some  form  of  design. 
Pale  brick.     Brick  which  are  underburned. 
Panel.     See  Key. 

Paving  brick.    Vitrified  brick  used  for  paving  purposes. 
Pegmatite.    A  coarse-grained  phase  of  granite.     It  often  occurs  as  dikes  or  lenses 

in  granites  or  metamorphic  rocks. 
Peridotite.     A  granular  intrusive  igneous  rock  composed  of  olivine  and  pyroxene 

without  feldspar. 
Phenocryst.    Isolated  or  individual  crystals,  usually  visible   to   the  naked   eye, 

which  are  embedded  in  a  finer  grained  ground  mass  of  igneous  rock. 
Phlogopite.     A  nearly  colorless  mica,  resembling  muscovite,  which  is  not  uncommon 

in  crystalline  limestones  and  serpentines. 

Phyllite.     A  metamorphic  rock  intermediate  between  a  slate  and  schist. 
Pipe  clay.     A  loosely  used  term  applied  to  smooth,  plastic  clays,  but  specifically 

referring  to  clays  for  making  sewer  pipe. 
Pipe  press.    The  name  commonly  applied  to  the  machine  used  for  molding  sewer 

pipe. 

Pisolitic.    Made  up  of  rounded  concretions  of  about  the  size  of  a  pea. 
Plagioclase.     A  collective  name  to  include  the  lime-soda  feldspars.     See  Feldspar. 
Plasticity.    The  property  possessed  by  clay  of  forming  a  plastic  mass  when  mixed 

with  water. 
Platting.    Brick  laid  flatwise  on  top  of  a  scove  kiln  to  keep  in  the  heat. 


GLOSSARY  397 

Plutonic.     A  term  referring  to  those  igneous  rocks  which  have  cooled  some  distance 

below  the  surface  and  show  usually  a  granitic  texture. 
Pompeiian  brick.     A  loosely  used  term,  but  it  is  probably  most  frequently  applied 

to  bricks  12  by  i£  by  4  inches  in  size,  of  medium  dark  shade,  with  a  brownish 

body  covered  with  iron  spots. 

Porphyritic.     A  structure  found  in  igneous  rocks,  indicating  the  presence  of  in- 
dividual crystals  (phenocrysts)  in  a  finer  grained  ground  mass. 
Post.     A  mass  of  slate  traversed  by  so  many  joints  as  to  be  useless. 
Pressed  brick.     A  loosely  used   term,  applied   to  smooth-faced  brick,  commonly 

employed  for  fronts. 
Pudding  stone.     See  Conglomerate. 
Pugging.     Same  as  Tempering. 

Pug  mill.     A  machine  for  mixing  or  tempering  wet  clay. 
Pumice.     A  name  applied  to  a  light,  porous  mass  of  volcanic  glass. 
Pyrite.     A  sulphide  of  iron  (FeS2)  easily  recognized  by  its  yellow  color  and  metallic 

lustre.     It  weathers  to  limonite.     A  not  uncommon  but  undesirable  constitu- 
ent of  many  rocks. 
Pyroxene.     Includes  several  mineral  species  of  the  same  general  composition  as 

amphibole,  but  differing  in  crystal  form.     Its  hardness  is  usually  5  to  6.     In 

small  grains  often  indistinguishable  from  amphibole. 
Quarry  water.     The  water  found  in  the  pores  of  stone  when  first  quarried. 
Quartz.     Chemically  this  is  silica.     It  has  a  hardness  of  7,  glassy  lustre,  conchoidal 

fracture  and  no  cleavage.     It  is  a  common  constituent  of  many  igneous  rocks 

and  sandstones. 
Quartz  monzonite.     An  igneous  rock  of  granitic  texture,  containing  quartz  with 

orthoclase  and  plagioclase  in  about  equal  proportions. 
Quartz  porphyry.     A  porphyritic  rock  having  the  same  mineral  composition  as 

granite,  and  with  quartz  occurring  as  a  phenocryst. 
Quartzite.     A  hard,  siliceous  rock,  usually  of  metamorphic  character  and  differing 

from  sandstone  in  being  harder  and  denser. 
Repressed  brick.     Bricks  which  have  been  put  through  a  second  pressing  machine 

after  molding,  to  improve  their  shape,  etc. 
Residual  clay.     One  formed  by  the  decay  of  rock  in  place.     This  type  is  abundant 

in  the  southern  states. 
Rhyolite.     A  volcanic  rock  of  the  same  general  mineralogical  composition  as  granite, 

but  which  usually  shows  a  porphyritic  texture.     It  may  be  quite  porous. 
Ribbons.     Bands  which  show  on  the  cleavage  surface  of  the  slate  and  indicate  lines 

of  bedding. 

Ridge  roll.     A  curved  piece  for  covering  ridge  of  roof  laid  with  roofing  tile. 
Ridge  tile.     A  roofing  tile  having  the  upper  half  flattened  to  a  plane,  and  used  at 

the  roof  ridge.     It  is  covered  by  a  finishing  tile. 

Ridge  T.    Used  in  roof  tiling  to  indicate  a  trimming  piece  for  use  at  the  inter- 
section of  two  ridges. 
Ridging.     See  Cresting. 
Rift.     A  microscopic  cleavage  in  granite,  which  greatly  aids  in  the  quarrying  of 

this  stone. 

Ring  pit.    A  circular  pit  in  which  there  revolves  a  large  wheel ;  used  for  tempering  clay. 
Rock-face  brick.    Those  with  surface  chiseled  to  imitate  cut  stone. 


398  BUILDING  STONES  AND   CLAY-PRODUCTS 

Roman  tile  or  brick.     Brick  usually  either  dry  pressed  or  stiff -mud  repressed,  and 

12  by  1 1  by  4  inches  in  size.     The  term  is  not  always  very  definitely  used. 
Roofing  tile.     Burned-clay  tile  used  for  covering  roofing. 
Run.     A  term  indicating  the  course  of  the  rift. 
Saccharoidal.     A  texture  or  grain  like  that  of  loaf  sugar. 
Salmon  brick.     See  Pale  brick. 
Salt  glaze.     A  glaze  seen  on  sewer  pipe  and  some  kinds  of  stoneware,  produced 

by  placing  salt  in  the  kiln  fires  during  burning. 

Sandstone.     A  sedimentary  rock,  normally  composed  chiefly  of  sand  grains. 
Sap.     An  iron  discoloration  along  joint  surfaces  in  rocks. 

Schist.     A  metamorphic  rock  made  up  chiefly  of  scaly  mineral  particles,  like  mica, 
which  are  arranged  in  a  more  or  less  parallel  position  and  hence  give  the  rock 
an  irregular  foliated  or  laminated  structure. 
Schistose.     Having  the  structure  of  a  schist. 

Scove  kiln.     A  temporary  kiln,  often  used  for  burning  common  brick. 
Sculp.    The  breaking  of  slate  preparatory  to  splitting.     It  is  usually  done  along 

the  grain. 

Seam.     Same  as  Joint. 
Sedimentary  rocks.     Those  usually  deposited  under  water,  and  having  a  stratified 

structure. 

Selenite.     A  transparent  crystalline  variety  of  gypsum. 
Semi-dry-press  process.     Practically  the  same  as  dry  press,  but  clay  may  be  slightly 

moister. 

Sericite.     A  term  applied  to  fine-grained,  fibrous,  white  mica  or  muscovite. 
Serpentine.     A  mineral  composed  of  hydrous  silicate  of  magnesia.    The  same  name 

is  applied  to  rocks  made  up  chiefly  of  this  mineral. 
Settle.     A  term  used  to  indicate  the  amount  of  vertical  fire  shrinkage  that  takes 

place  in  a  kiln  full  of  bricks. 

Seiver  brick.     A  general  term  applied  to  those  common  brick  which  are  burned  so 
hard  as  to  have  little  or  no  absorption.     They  are,  therefore,  adapted  for  use 
as  sewer  linings. 
Shale.     A  consolidated  clay. 
Shaly.     A  term  applied  to  thinly  bedded  rocks,  which  break  up  into  thin  layers 

like  shale. 
Sheet  quarry.     A  term  often  used  in  granite  quarrying,  to  designate  a  quarry  having 

strong  horizontal  joints  and  few  vertical  ones. 
Shelly.     Same  as  Shaly. 
Shingle  tile.     A  flat  form  of  roofing  tile. 

Shrinkage.     The  decrease  in  volume  which  clays  undergo  in  drying  and  burning. 
Siding  tile.     Any  roofing  tile  employed  for  upright  work. 
Siliceous.     Containing  appreciable  silica  as  an  impurity;    for  example,  a  siliceous 

limestone. 
Slate.     A  metamorphic  rock  derived  usually  from  shale  and  clay.     It  generally  has 

a  well-developed  cleavage. 
Slickensides.     Polished  and  grooved  surfaces,  caused  by  one  mass  of  rock  in  the 

earth's  crust  sliding  past  another,  as  happens  in  faulting. 

Slip  clay.     An  easily  fusible  clay,  sometimes  used  to  make  a  natural  glaze  on  the 
surface  of  clay  wares. 


GLOSSARY  399 

Slip  glaze.     One  produced  with  slip  clay  (q.  v.). 

Slop  brick.    A  name  sometimes  applied  to  soft-mud  brick. 

Soak  pit.     A  pit  in  which  wet  clay  is  allowed  to  soak  preparatory  to  molding. 

Soft-mud  process.     A  method  of  molding  brick,  by  forcing  clay  into  wooden  molds. 

Spanish  tile.     Roofing  tile  having  an  S-shaped  cross  section. 

Specific  gravity.    The  weight  of  a  substance,  as  compared  with  an  equal  volume 

of  distilled  water. 

Stalactite.     A  carbonate  of  lime  deposit  formed  on  the  roof  of  limestone  caves. 
Stalagmite.     A  carbonate  of  lime  deposit  built  up,  usually  in  columnar  forms,  on 

the  floor  of  caves. 
Starter.  See  Eave  tile. 
Stiff-mud  process.  A  plastic  method  of  molding  brick  by  forcing  the  clay  through 

a  die. 

Stock  brick.    The  better  or  selected  bricks  of  a  kiln. 
Stratified  rocks.     Those  rocks  which  occur  in  layers  or  beds  and  are  of  sedimentary 

origin. 

Stretcher.     A  brick  or  stone  laid  with  its  length  parallel  to  the  face  of  the  wall. 
Strike.     A  term  applied  to  stratified  or  metamorphic  rocks  to  indicate  the  direction 

in  which  the  tilted  beds  extend. 

Stripping.     Worthless  material  which  has  to  be  removed  in  quarrying. 
Syenite.     An  igneous  rock  closely  allied  to  granite,  but  differing  from  it  in  not 

containing  quartz. 
Syenite  porphyry.  A  rock  of  porphyritic  texture  and  same  mineral  composition 

as  syenite. 

Syncline.     A  trough -like  fold. 
Talc.     A  hydrous  silicate  of  alumina,  magnesia  and  iron.     Hardness  i,  feel  greasy, 

and  structure  usually  foliated.     Soapstone  is  a  massive  impure  form  of  talc, 

of  no  value  as  a  building  stone,  but  used  for  table  tops,  sinks,  tubs,  etc. 
Tapestry  brick.     These  are  brick  made  by  the  stiff-mud  process  and  having  all 

surfaces  roughened  by  wire  cutting.     Much  used  now  for  exteriors. 
Tempering.     The  process  of  mixing  clays  preparatory  to  molding  them. 
Terra-cotta  clay.     A  loose  term  that  might  include  any  clay  used  in  the  manufacture 

of  terra  cotta. 
Terra-cotta  lumber.     A  name  applied  to  fireproofing  shapes,  which  are  very  porous 

and  somewhat  soft. 
Toe  nails.     Defined  by  Dale  as  "Curved  joints  intersecting  the  sheet  structure, 

in  most  cases  striking  with  the  sheets,  in  some  differing  from  them  in  strike 

45  degrees  or  more." 

Trachyte.     A  volcanic  rock  having  the  same  mineral  composition  as  syenite. 
Trap.     A  name  often  applied  to  diabase  and  sometimes  to  basalt. 
Travertine.     A  calcareous  rock,  deposited  by  spring  or  swamp  waters.     It  is  usually 

very  porous. 
Tremolite.     A  variety  of  amphibole  (q.  v.)  found  as  an  injurious  impurity  in  some 

magnesian  marbles. 
Updraft  kiln.    One  in  which  the  heat  enters  the  kiln  chamber  from  the  bottom  and 

passes  up  through  the  ware. 

Valley  tile.     Roofing  tile  made  to  fit  in  the  valley  of  a  roof. 
Verde  antique.    A  green  rock,  usually  a  mixture  of  serpentine  and  calcite. 


400  BUILDING  STONES  AND  CLAY-PRODUCTS 

Vesicular.     See  Cellular. 

Volcanic  ash.  A  deposit  of  loose,  fine-grained  volcanic  glass  ejected  during  volcanic 
eruptions.  In  its  consolidated  form  it  may  be  used  for  building  stone. 

Volcanic  tuff.     A  deposit  of  volcanic  ash  which  has  become  consolidated. 

Volcanic  rocks.  Those  igneous  rocks  which  have  reached  the  surface  before  cool- 
ing and  solidifying. 

Weathering.  The  breaking  down  of  a  rock  when  exposed  to  the  action  of  weather- 
ing agents. 

Whitewash.  A  white  scum  of  soluble  sulphates  which  accumulates  on  the  surface 
of  a  brick  or  other  clay  product  during  or  after  manufacture. 

Wall  white.     A  white  scum  that  appears  on  bricks  after  they  are  set  in  the  wall. 


INDEX 


A. 

Abrasive  action  of  wind  on  stone,  70. 
Abrasive  resistance  of,  building  stone, 
70. 

slate,  230. 
Absorption  of,  brick,  296. 

building  stone,  44. 

floor  tile,  366. 

limestones,  181. 

marbles,  201. 

roofing  tile,  355. 

sandstones,  163. 
Absorption  test  of  brick,  296. 
Acids,  effect  on  weathering  of  stone,  85. 
Adams  County,  111.,  191. 
Addison,  Me.,  granite  described,   109, 

in. 

jEolian  marble,  213. 
Air  brick,  defined,  259. 
Alabama,  granites  of,  155.. 

limestones  of,  190. 

marbles  of,  223. 

sandstones  of,  170. 
Alabama-Iris  marble,  223. 
Alabama-Sunset  marble,  223. 
Alabaster,  defined,  10. 
Alfred,  Me.,  in. 
Amberg,  Wis.,  granite  described,   100, 

IS?- 
American  Pavonazzo  marble,  213. 

yellow  Pavonazzo  marble,  214. 
Amherst,  O.,  173. 
Amphibole,  defined,  9. 
Analyses  of,  clay,  258. 

limestones,  183. 

sandstones,  164. 
Andesitein,  Colorado,  161. 

Oregon,  161. 
Aragonite,  defined,  10. 
Arbuckle    Mountains,    Okla.,    granites 
described,  159. 


Arch  brick,  defined,  259. 

Architectural    terra    cotta    (see    Terra 

Cotta}. 
Arizona,  marbles  of,  223. 

onyx  marbles,  250. 

opal  marble,  223. 

Pavonazzo  marble,  224. 
Arkansas,  sandstones  of,  176. 

slates  of,  241. 

syenites  described,  159. 

tests  of  slate  from,  233. 
Arkins,  Colo.,  177. 
Arkose,  defined,  29,  165. 
Arvonia,  Va.,  241. 
Ash,  volcanic,  17. 
Ashlar  brick,  defined,  259. 
Athenian  Green  serpentine,  249. 
Auburn,  N.  H.,  granite  described,  112. 
Augite,  defined,  9. 
Ausable  Forks,  N.  Y.,  granite,  137. 
Austin,  Tex.,  197. 

chalk,  197. 
Avondale,  Pa.,  216. 

B. 

Bangor,  Pa.,  238,  241. 

Barley  ville,  Me.,  in. 

Barre,  Vt.,  granite  described,  105,  116. 

Basalt,  in  Oregon,  161. 

characters  of,  24. 

porphyry,  defined,  24. 
Bate  or  false  cleavage,  defined,  226. 
Bathylith,  defined,  17. 
Bayfield,  Wis.,  175. 
Becket,  Mass.,  100. 
Bedding,  defined,  32. 

effect  of,  on  quarrying,  32. 
Bedford,  Indiana,  limestone,  191. 
Beebe,  cited,  298,  301,  309. 
Belfast,  Me.,  in. 
Belfast,  Pa.,  241. 


401 


402 


INDEX 


Bellingham,  Wash.,  177. 

Belleville,  N.  J.,  168. 

Bellvue,  Colo.,  177. 

Berea,  O.,  sandstone,  170. 

Berea,  O.,  173. 

Berlin,  Wis.,  granite  described,  100,  156. 

Bethel,  Vt.,  granite  described,  116. 

Bibb  County,  Ala.,  190. 

Biddeford,  Me.,  no. 

Biotite,  denned,  8. 

Black  granites,  denned,  99. 

Black  Island,  Me.,  no. 

Blue  Hill,  Me.,  106,  no,  in. 

Black  marble,  216. 

Blue  Hill,  Me.,  uses  of  granite  from,  no. 

Bluestone,  denned,  165. 

in  New  York,  168. 

in  Pennsylvania,  169. 
Book  tiles,  denned,  333. 
Bosses,  denned,  17. 
Bowling  Green,  Ky.,  192. 
Bradbury,  Me.,  in. 
Brandon,  Vt.,  202. 

Italian  marble,  207. 
Branford,  Conn.,  100. 

township,   Conn.,  granite  described, 

131- 

Branner,  J.-C.,  cited,  176. 
Brecciated  structure,  in  marbles,  198. 
Brick,  building,  raw  materials  used,  263. 
specifications  for  testing,  307. 

burning  of,  279. 

comparison  of  different  processes,  283. 

drying  of,  276. 

kinds  of,  259. 

methods  of  manufacture,  264. 

repressing  of,  276. 

requisite  qualities  of,  314. 

scumming  of,  312. 

testing  of,  284. 

kilns,  279. 

Brickotta,  defined,  317. 
Bridgeport,  Wis.,  195. 
Broad  Creek,  Md.,  249. 
Brocadillo  marble,  207. 
Brookline,  N.  H.,  in. 
Brookville,  Me.,  uses  of  granite  from, 

1 10. 


Brownstone,  defined,  165. 

in  New  Jersey,  168. 
Brunswick,  Me.,  111. 
Buckley,  E.  R.,  cited,  40,  43,  50,  51,  52, 

55,  79,  94,  95,  155,  192. 
Building  stone,  abrasive  resistance  of, 

70. 
work  of  wind  on,  80. 

absorption  of,  44. 

chemical  composition  of,  75. 

color,  37. 

color,  change  in,  38. 

contraction  of,  69. 

crushing  strength  of,  44. 

decomposition  on  weathering,  81. 

discoloration,  73. 

disintegration  of,  76. 

effect  of  acid  gases  on,  74. 

effect  of  carbonic  acid  gas  on,  74. 

effect  of  careless  quarrying,  80. 

effect  of  freezing  on,  79. 

effect  of  plants  on,  80. 

effect  of  water  on,  81. 

effect  of  temperature  changes  on,  76. 

expansion  of,  69. 

fire  resistance  of,  55. 

frost  resistance  of,  54. 

hardening  on  exposure,  85. 

hardness  of,  36. 

life  of,  86. 

literature  on,  87. 

permanent  swelling,  69. 

polish  of,  40. 

porosity  of,  40. 

properties  of,  36. 

quarry  water  in,  44. 

sap  of,  87. 

soluble  salts  in,  85. 

texture  of,  36. 

transverse  strength  of,  51. 

weathering  of,  75. 
Burnet  County,  Tex.,  100, 160. 
Byram,  N.  J.,  168. 


Cabot,  Vt,  116. 
Calais,  Me.,  in. 
Calais,  Vt.,  116. 


INDEX 


403 


Calcareous  tufa,  defined,  30. 

Calcite,  effect  of,  in  building  stones,  10. 

in  slate,  226. 

properties  of,  10. 
Calc  sinter,  defined,  184. 
Calhoun  County,  Ala.,  190,  223. 
Calico  marble,  217. 
California,  granites  of,  161. 

marbles  of,  224. 

onyx  marbles,  250. 

sandstones  of,  177. 

serpentine,  249. 

slates  of,  242. 
Canaan,  N.  H.,  in. 
Cannelton,  Ind.,  174. 
Canyon  City,  Colo.,  177. 
Carbon,  effect  of,  on  clay,  257. 

in  marble,  198. 

Carbonic  acid  gas,  effect,  of,  on  building 
stone,  74. 

test,  of  building  stone,  75. 
Cardiff,  Md.,  241. 
Carrara  marble,  texture,  36. 
Carroll  County,  111.,  174. 
Carthage,  Mo.,  196,  223. 
Castle  Rock,  Colo.,  160. 
Chalk,  denned,  30,  183. 
Champlain  marbles,  214. 
Chapman,  Pa.,  241. 
Charlotte,  N.  C.,  150. 
Chazy,  N.  Y.,  216. 

Chemical     composition     of,     building 
stone,  75. 

granite,  95. 

Chemical  Composition  (see  also  Anal- 
yses). 

Cherokee,  Ala.,  170. 
Cherokee  County,  N.  C.,  217. 
Cherokee  marbles,  218. 
Chert,  defined,  7. 

in  limestones,  181. 
Chester,  Mass.,  granite,  120,  125. 
Chester,  N.  J.,  168. 
Chimney  rock,  191. 
Chlorite,  defined,  n. 
Cipolino  marble,  weathering  of,  87. 
Clark's  Island,   Me.,   uses   of  granite 
from,  no,  in. 


Classification  of  granites,  95. 

Connecticut,  133. 

Maine,  no. 

Massachusetts,  125. 

New  Hampshire,  113. 
Clay,  analyses  of,  258. 

chemical  properties,  256. 

color  after  burning,  257. 

in  slate,  229. 

physical  properties  of,  253. 

properties  of,  253. 
Cleavability  of  slate,  229. 
Cleavage,  of  minerals,  defined,  6. 

of  rocks,  defined,  30. 
Clinker  brick,  defined,  259. 
Coal  Measures,  sandstones,  Alabama, 
170. 

Indiana,  173,  174. 

Michigan,  174. 

Pennsylvania,  169. 
Cockeysville,  Md.,  216. 
Colbert  County,  Ala.,  190. 
Cold  Springs,  Okla.,  159. 
Colorado,  andesite  in,  161. 

gneisses,  160. 

granites  described,  160. 

limestones  of,  197. 

marbles  of,  223. 

rhyolite  in,  160. 

sandstones  of,  176. 
Color,  building  stone,  cause  of,  37. 

change  of,  38. 

variation  in,  38. 
Color  of,  building  stone,  37. 

sandstones,  163. 

slate,  229. 

Columbia,  S.  C.,  granite  described,  153. 
Columbia  Listavena  marble,  214. 
Columbus,  Mont.,  176. 
Colusa  County,  Calif.,  177. 
Common  brick,  requisite  qualities  of} 

314- 

Compass  brick,  defined,  260. 
Concord,  N.  H.,  granite  described,  in. 
Conglomerate,  characters  of,  29. 
Connecticut,  granites  of,  128. 

marbles  of,  215. 

sandstones  of,  166. 


404 


INDEX 


Continuous  kilns,  280. 
Contraction  of  building  stone,  69. 
Con  way,  N.  H.,  granite  described,  112. 
Conyers,  Ga.,  granites,  154. 
Cook  County,  111.,  191. 
Coosa  County,  Alabama,  223. 
Coquina,  denned,  30,  183. 

occurrence,  191. 
Cordilleran  region,  granites  of,  160. 

limestones  of,  197. 
Cornwall,  Mo.,  158. 
Corona,  Calif.,  161. 
Corrodibility  of  slate,  230. 
Cotopaxi,  Colo.,  160. 
Cotton-rock,  Mo.,  196. 
Cranberry    Lake,    N.    J.,    granite   de- 
scribed, 138. 
Creole  marble,  218. 
Cresting  tile,  361. 
Crosby,  W.  O.,  cited,  244. 
Cross  fracture,  of  slate,  229. 
Crotch  Island,  Me.,  no,  in. 

granite  described,  106. 
Crushing  test  of  brick,  284. 
Crushing  strength  of,  brick,  wet  and  dry 
compared,  294. 

building  stone,  44. 

floor  tile,  370. 

granites,  94 

limestones,  181. 

marbles,  201. 

sandstones,  163. 
Crystal  form  of  minerals,  6. 
Cullman,  Ala.,  170. 
Cut-off,  denned,  96. 

in  granite,  96. 
Cuyahoga  County,  O.,  173. 


D. 


Dale,  T.  N.,  cited,  94,  96,  99,  in,  113, 

116,  132,  136,  233. 
Danielsville,  Pa,,  241. 
Dark  Florence  marble,  213. 
Dark  Vein  Esperanza  marble,  213. 
Deer  Isle,  Me.,  no. 
Dedham,  Me.,  in. 
De  Kalb  County,  Ala.,  190. 


Del  Norte,  Colo.,  161. 
Derby,  Vt,  116. 
Dikes,  defined,  17. 

in  granite,  99. 
Dillon,  Mont.,  160. 
Diorite,  characters  of,  23. 

porphyry,  denned,  24. 
Discoloration  of  building  stone,  73. 
Discoloration  test,  building  stone,  73. 
Distribution  of  sandstones,  166. 
Dix  Island,  Me.,  uses  of  granite  from, 

no. 
Dolomite,  defined,  183. 

properties  of,  10. 

as  building  stones,  178. 

properties  of  (see  under  Limestones). 
Dolomitic  limestone,  defined,  184. 
Dorset  Dark  Green  Vein  marble,  207. 
Dorset  Mountain,  Vt.,  202. 
Dorset  white  marble,  208. 
Douty,  cited,  298,  301,  309. 
Dover,  N.  J.,  granite  described,  138. 
Dry-press  brick,  properties  of,  275. 
Dry -press  process,  275. 
Dummerston,  Vt.,  116. 
Dunn's  Mountain,  N.  C.,  149. 
Dunnville,  Wis.,  174. 
Dutch  brick,  defined,  260. 

E. 

East  Bangor,  Pa.,  241. 
East  Canaan,  Conn.,  215. 
East  Cleveland,  O.,  173. 
East  Longmeadow,  Mass.,  167. 
Easton,  Pa.,  244. 
Eave  tile,  361. 

Edgecomb  County,  N.  C.,  146. 
Edwards  limestone,  Texas,  197. 
Efflorescence  of  brick,  312. 
Elasticity  of,  granites,  94. 

slate,  230. 

Elberton,  Ga.,  granite  described,  154. 
Eldorado  County,  Calif..  242. 
Electrical  resistance  of  slate,  230. 
Ellicott  City,   Md.,   granite  described 

141. 
Enameled  brick,  defined,  259. 

requisite  qualities,  317. 


INDEX 


405 


Essex  County,  N.  Y  ,  244. 
Etowah  County,  Ala.,  190. 

marble,  218. 
Euclid,  O.,  173. 

bluestone,  173. 

Expansion  of  building  stone,  69. 
Expansion  coefficient  of  brick,  305. 


F. 


Face  brick,  denned,  250. 

Fairburn,  Ga.,  granites,  154. 

Fairfield  County,  S.  C.,  100. 

Fall  River,  Mass.,  120. 

False  cleavage  in  slate,  denned,  226. 

Feldspar,  properties  of,  7. 

Felsite,  characters  of,  24. 

Finials,  361. 

Fire  brick,  denned,  260.  t 

Fireproofing,  denned  333. 

fire  tests  of,  346. 

properties  of,  334. 

specifications  for,  345. 

tests  of,  341. 
Fire  resistance  of,  building  stone,  55. 

granites,  95. 

limestones,  181. 

sandstones,  165. 

terra  cotta,  328. 
Fire  tests  of,  brick,  302. 

fireproofing,  346. 
Fisk  Black  marble,  213. 
Fitzwilliam,  N.  H.,  granite  described, 

III,   112. 

Flagstones,  Colorado,  177. 

defined,  166. 

New  Jersey,  168. 

New  York,  168. 
Flashed  brick,  defined,  260. 
Flexibility  of  granite,  94. 
Flint,  defined,  7. 

in  limestone.  196. 
Floor  tile,  manufacture  of,  366. 

properties  of,  365. 

testing  of,  369. 
Florence  marble.  208. 
Florentine  blue  marble,  213. 
Florida,  limestones  of,  191. 


Foerster,  cited,  43. 

Fourche  Mountain,  Ark.,  159. 

Fox  Island,  Me.,  granite  described,  109. 

Franklin  County,  Ala.,  190. 

Frankfort,  Me.,  in. 

Fredericksburg,  Va.,  granite  described, 

145- 

Frederick  town,  Mo.,  158. 
Freeport,  Me.,  in. 
Freestone,  defined,  166. 
Freezing,  effect  of,  on  building  stone,  79. 
Freitag,  cited,  302,  328,  331,  337,  338, 

339,  347- 

Frenchtown,  Md.,  granite  gneiss,  142. 
Front  brick,  defined,  259. 
Frost  resistance  of  building  stone,  54. 
Frost  test  of,  brick,  305. 

building  stone,  artificial,  54. 

natural,  54. 
Fryeburg,  Me.,  in. 
Furring  blocks  defined,  333. 

sizes  made,  338. 
Furring  brick,  defined,  260. 
Fusibility  of  clay,  255. 


G. 


Gabbro,  characters  of,  23. 

of  California,  161. 

of  North  Carolina,  150. 
Garnet,  properties  of,  n. 
Gary,  cited,  70,  73. 
Genessee,  Wis.,  195. 
Georgia,  granites  of,  154. 

marbles  of,  218. 

serpentine  of,  249. 

slates  of,  241. 

German    Valley,    N.    J.,    granite    de- 
scribed. 138. 

Gladson,  W.  M.,  cited,  231. 
Glazed  brick,  defined,  259. 
Glens  Falls,  N.  Y.,  216. 
Gneiss,  defined,  31. 

Gneisses,  distribution  in  United  States, 
105. 

of  Maryland,  142. 

of  New  Jersey,  137. 
Gouverneur,  N.  Y.,  216. 


406 


INDEX 


Graduated  roofing  tile,  361. 
Grady,  R.  F.,  cited,  324. 
Grain  in  slate,  defined,  226. 
Grain  of  granite,  96. 
Granite  as  a  rock,  properties  of,  18. 
Granite  City,  Okla.,  100,  159. 
Granite  diorite,  defined,  23. 
Granite  Heights,  Wis.,  100. 
Granite  porphyry,  defined,  23. 
Granites,  black,  99. 

characteristics  of,  94. 

chemical  composition  of,  95. 

classification  of,  95. 

crushing  strength,  94. 

cut-off  in,  96. 

dikes  in,  99. 

distribution  in  United  States,  105. 

elasticity  of,  94. 

expansion  of,  95. 

fire  resistance  of,  95. 

flexibility  of,  94. 

grain  of,  96. 

inclusions  in,  99. 

joints  in,  96. 

knots  in,  96. 

market  price  of,  136. 

mineral  impurities  in,  94. 

of  Alabama.  155, 

of  California,  161. 

of  Colorado,  160. 

of  Connecticut,  128. 
classification  of,  133. 

of  Cordilleran  area,  160. 

of  eastern  belt,  105. 

of  Georgia,  154. 

of  Maine,  classification  of,  no. 

of  Maine,  106. 

of  Maryland,  138. 

of  Massachusetts,  120. 

of  Minnesota,  157. 

of  Missouri,  158. 

of  Montana,  160. 

of  New  Hampshire,  in. 
classification  of,  113. 

of  New  Jersey,  137. 

of  New  York,  137. 

of  North  Carolina,  145. 

of  Oklahoma,  159. 


Granites,  of  Rhode  Island,  128. 

of  South  Carolina,  150. 

of  Texas,  160. 

of  Vermont,  116. 

of  Virginia,  142. 

of  Wisconsin,  155. 

porosity  of,  95. 

porphyritic,  North  Carolina,  149. 

rift  of,  96. 

run  of,  96. 

sheets  in,  96. 

specific  gravity  of,  94. 

structure  of,  96. 

tests  of,  99. 

uses  of,  105. 

weight  per  cubic  yard,  94. 
Graniteville,    Mo.,    granite    described, 

100,  158. 

Granville,  N.  Y.,  238. 
Graywacke,  defined,  166. 
Gregory,  H.  E.,  cited,  132. 
Greenbrier  County,  W.  Va.,  190. 
Green  Island,  Me.,  no. 
Greenville,  Ga.,  granite,  154. 
Greenwich,    Conn.,    granite   described, 

131- 
Greystone,  N.  C.,  granite  described, 

149. 
Groton,  Conn.,  granite  described,  116, 

132. 
Guilford,  Md.,  granite  described,  no, 

141. 
Gypsum,  properties  of,  10. 

H. 

Hagerstown,  Md.,  190. 

Hallowell,  Me.,  granite  described,  106, 

in. 

Hampton,  N.  Y.,  238. 
Hannibal,  Mo.,  196. 
Hardening  of  building  stone,  85. 
Hardness,  of  building  stone,  36. 

of  sandstones,  162. 
Hardness  scale  of  minerals,  6. 
Hardness,  test  of,  37. 
Hard  vein  slate,  238. 

Pennsylvania,  238. 


INDEX 


407 


Hardway,  defined,  96. 

Hardwick,  Vt.,  granite  described,  116. 

Hartland,  Me.,  in. 

Hawes,  G.,  cited,  37. 

Heath  Springs,  S.  C.,  granite  described, 

i53- 

Helderberg  limestone,  N.  Y.,  189. 
Helena,  Mont.,  160. 
Henry  County,  111.,  174- 
Hermann,  cited,  40. 
Hermon,  Me.,  in. 
Hip  rolls,  361. 
Hip  roll  starters,  361. 
Hip  tile,  360. 
Hollow  blocks,  defined,  333. 

sizes  of,  339. 

tests  of,  340. 

Hollow  brick,  defined,  260,  333. 
Hollow  ware,  manufacture  of,  333. 

raw  materials  used,  333. 
Holly  Springs,  Ga.,  249. 
Hornblende,  properties  of,  9. 
Hudson  River  Bluestone,  168. 
Hummelstown,  Pa.,  169. 
Humphrey,  R.  L.,  cited,  56. 
Hunterdon  County,  N.  J.,  168. 
Hurricane    Island,    Me.,    granite    de- 
scribed, 109. 

I. 

Igneous  rocks,  defined,  13. 

classification  of,  18. 

distribution  in  United  States,  105. 

texture  of,  17. 

used  for  building,  93. 
Illinois,  limestones  of,  191. 

sandstones,  174. 
Inclusions  in  granite,  99. 
Index,  Wash.,  100. 
Indiana,  limestones  of,  191. 

sandstones  of,  173. 
Interlocking  tile,  defined,  351. 
Inyo  County,  Calif.,  224. 
Iowa,  limestones  of,  196. 
Iron  oxide,  effect  on  clay,  256. 
Iron  pyrite  (see  Pyrite). 
Italic  marble,  208. 


J. 

Jacobsville,  Mich.,  174. 
Jasper,  Ala.,  170. 

marble,  214. 
Jay,  Me.,  in. 
Jefferson  City,  Mo.,  196. 
Jefferson  County,  Ala.,  190. 
Jointing,  defined,  32. 

effect  of,  on  quarrying,  32. 

in  granite,  96. 
Joints  in  slate,  226. 
Joliet,  111.,  191. 
Jones,  J.  C.,  cited,  298,  306. 
Jonesboro,  Me.,  granite  described,  no. 
Jonesport,  Me.,  no. 
Julien,  A.  A.,  cited,  86. 

K. 

Kaiser,  E.,  cited,  85. 

Kankakee  County,  111.,  191. 

Kansas,  limestones  of,  196. 

Kasota,  Minn.,  195. 

Keeler,  Calif.,  224. 

Kennebunkport,,  Me.,  no. 

Kentucky,  limestones  of,  192. 

Kettle    River    sandstone,    Minnesota, 

175- 
Key  West,  Fla.,  191. 
Kibbe,  Mass.,  167. 
Kirby,  Vt.,  116. 

Kittatinny  Mountain,  N.  J.,  168. 
Knob  Lick,  Mo.,  granite  described,  158. 
Knobstone  sandstone,  Indiana,  173. 
Knots,  defined,  96. 
Knowles,  Wis.,  195. 


L. 


Lancaster  County,  Pa.,  189. 
Landscape  Green  serpentine,  249. 
Lannon,  Wis.,  195. 
Lawrence  County,  Ind.,  191. 
Lawrenceville,  Ga.,  granites,  154. 
Lawrenceville,  N.  J.,  168. 
Lebanon,  N.  H.,  in. 
Lee,  Mass.,  215. 
Lehigh  County,  Pa.,  238. 


408 


INDEX 


Lemont,  HI.,  191. 

Lenox  Library,  N.  Y.  City,  87. 

Lepanto  marble,  216. 

Lewis  and  Clarke  County,  Mont.,  160. 

Lexington,  Ga.,  154. 

Lexington,  N.  C.,  150. 

Life  of  building  stone,  86. 

Light  Cloud  Rutland  marble,  207. 

Lime,  effect  on  clay,  256. 

in  slate,  229. 
Limestone,  fossiliferous,  denned,  183. 

hydraulic,  denned,  183. 
Limestones,  absorption  of,  181. 

as  building  stone,  178. 

characters  of,  29. 

chemical  composition  of,  183. 

color  of,  178. 

crushing  strength  of,  181. 

distribution  in  United  States,  184. 

fire  resistance  of,  181. 

hardness  of,  178. 

of  Alabama,  190. 

of  Cordilleran  region,  197. 

of  Florida,  191. 

of  Illinois,  191. 

of  Indiana,  191. 

of  Iowa,  196. 

of  Kansas,  196. 

of  Kentucky,  192. 

of  Maryland,  190. 

of  Minnesota,  195. 

of  Missouri,  196. 

of  New  Jersey,  189. 

of  New  York,  189. 

of  Ohio,  192. 

of  Pennsylvania,  189. 

of  Texas,  197. 

of  Virginia,  190. 

of  West  Virginia,  190. 

of  Wisconsin,  192. 

tests  of,  181. 

texture  of,  178. 

varieties  of,  183. 

weathering  qualities,  181. 
Limonite,  properties  of,  12. 
Lincoln,  Me.,  in. 
Lincoln  County,  Me.,  106. 
Listavena  marble,  208. 


Lithographic  limestone,  denned,  183. 

Lithonia,  Ga.,  granites,  100,  154. 

Little  Falls,  N.  J.,  168. 

Little  Rock,  Ark.,  100,  159. 

Llano  County,  Tex.,  100,  160. 

Lockport,  N.  Y.,  167,  189. 

Long  Cove,  Me.,  in. 

Lower  Carboniferous  limestone,  Mis- 
souri, 196. 

Lower  Magnesian  limestone,  Wisconsin, 
192,  195. 

Luquer,  L.  McL,  cited,  54. 

Lustre,  of  minerals,  denned,  6. 

Lyonnaise  marble,  214. 

M. 

Machias,  Me.,  uses  of  granite  from,  no. 
Mackler,  cited,  313. 
Madison  County,  111.,  191. 
Magnesian  limestone,  denned,  184. 
Magnetite,  properties  of,  12. 
Maiden  Rock,  Wis.,  195. 
Maine,  granites  described,  106. 

slates  of,  237. 
Manitou  stone,  Colo.,  177. 
Mankato,  Minn.,  195. 
Mansfield  sandstone,  Ind.,  173. 
Marble,  defined,  184. 
Marblehead,  Wis.,  195. 
Marble,  absorption  of,  201. 

characters  of,  31. 

color  of,  198. 

mineral  composition,  197. 

properties  of,  197. 

strength  of,  201. 

texture  of,  198. 

uses  of,-2oi. 

weathering  qualities  of,  201. 
Marbles,  distribution  in  United  States, 
202. 

of  Alabama,  223. 

of  Arizona,  223. 

of  California,  224. 

of  Colorado,  223. 

of  Connecticut,  215. 

of  Georgia,  218. 

of  Maryland,  216. 


INDEX 


409 


Marbles,  of  Massachusetts,  215. 

of  Missouri,  223. 

of  New  York,  215. 

of  North  Carolina,  217. 

of  Pennsylvania,  216. 

of  Tennessee,  218. 

of  Virginia,  217. 

of  Vermont,  202. 
Marcasite,  denned,  12. 

in  slate,  230. 

Marini,  V.  G.,  cited,  345. 
Marlboro  Granite,  N.  H.,  in,  113. 
Marquette,  Mich.,  174. 
Marshall  County,  Ala.,  190. 
Marshfield,  Me.,  no. 
Martinsburg,  W.  Va.,  241. 
Martinsville,  N.  J.,  168. 
Maryland,  gneisses  of,  142. 

granites  described,  138. 

limestones  of,  190. 

marbles  of,  216. 

sandstones  of,  169. 

serpentine  of,  249. 

slates  of,  241. 
Mascoma,    N.    H.,    granite   described, 

"3- 

Massachusetts,    granites,    classification 

of,  125. 
described,  120. 

marbles  of,  215. 

sandstone  of,  166. 

serpentine  of,  244. 
Matthews,  E.  B.,  cited,  170. 
McCourt,  W.  E.,  cited,  56. 
Medina  sandstone,  167. 
Mena,  Ark.,  242. 
Menominee,  Wis.,  174. 
Merrill,  G.  P.,  cited,  9,  49,  54,  70,  87, 

95,  166,  177,  241,  244. 
Metamorphic  rocks,  characters  of,  30. 
Mexican  tile,  defined,  350. 
Miami,  Mo.,  176. 
Mica,  effect  of,  on  building  stone,  8. 

in  marble,  197. 
Micas,  properties  of,  8. 
Michelot,  cited,  51. 
Michigan,  sandstones  of,  1 74. 
Middlebury,  Vt.,  202. 


Milford,     Mass.,      granite     described, 

1 20. 
Milford,  N.  H.,  granite  described,  in, 

112. 

Millbridge,  Me.,  in. 
Millstone,    Conn.,    granite    described, 

131- 

Mineral  impurities  in  granite,  94. 
Minerals,  form  of,  6. 

hardness  of,  6. 

in  building  stones,  3. 

physical  properties  of,  5. 
Minnesota,  granites  of,  157. 

limestones  of,  195. 

sandstones  of,  175. 
Mission  tile,  defined,  350. 
Missouri,  granites  of,  158. 

limestones  of,  196. 

marbles  of,  223. 

sandstones  of,  176. 
Modern  Spanish  tile  defined,  350. 
Mohegan  granite,  N.  Y.,  137. 
Monroe  County,  Ind.,  191. 
Monson,  Me.,  237. 
Montana,  granites  of,  160. 

sandstones  of,  176. 

volcanic  ash  in,  160. 
Montello,  Wis.,  granite  described,  100, 

155- 

Montgomery  County,  Ark.,  241. 
Montgomery  County,  Pa.,  189. 
Monzonite,  defined,  23. 
Moose  Island,  Me.,  no. 
Moriah,  N.  Y.,  244. 
Mountain  white  marble,  208. 
Mount  Airy,  N.  C.,  100,  149. 
Mount  Ascutney,  Vt.,  116. 
Mount  Desert,  Me.,  no,  in. 
Muscovite,  defined,  8. 

N. 

Nash  County,  N.  C.,  146. 
Newark,  Vt.,  116. 
New  Bedford,  Mass.,  120. 
Newburgh,  O.,  173. 

New  Hampshire,  granites  of,  described, 
in. 


4io 


INDEX 


New  Jersey,  granites  of,  137. 

limestones  of,  189. 

sandstones  of,  168. 

serpentine  of,  244. 

slates  of,  238. 

Newman,  Ga.,  granite,  154. 
Newton,  N.  J.,  238. 
New  York,  granites  of,  137. 

limestones  of,  189. 

marbles  of,  215. 

sandstones  of,  167. 

serpentine  of,  244. 

slates  of,  238. 
New  Ulm,  Minn.,  176. 
Niagara  limestone  in,  Illinois,  191. 

New  York,  189. 

Wisconsin,  192,  195. 
Normal  tile,  defined,  350. 
Norman  tile,  defined,  260. 
Norridgewock,  Me.,  no,  in. 
Northampton  County,  Pa.,  238. 
North  Carolina,  granites  of,  145. 

marbles  of,  217. 

North  Jay,  Me.,  granite  described,  105, 
106. 

O. 

Oglesby,  Ga.,  granite  described,  154. 
Ohio,  limestones  of,  192. 

sandstones  of,  170. 
Oklahoma,  granites  described,  159. 
Old  Spanish  tile,  defined,  350. 
Olive  marble,  214. 
Olivine,  properties  of,  n. 
Olivo  marble,  214. 
Onyx,  defined,  30. 

marble,  defined,  249. 

marbles,  foreign,  250. 
in  United  States,  250. 

marble,  origin  of,  249. 

properties  of,  250. 
Oolitic  limestone,  Alabama,  190. 

defined,  184. 

Florida,  191. 

Indiana,  191. 

Kentucky,  192. 

West  Virginia,  190. 
Ophicalcite,  defined,  243. 


Ophiolite,  defined,  243. 
Oregon,  andesite  in,  161. 

basalt  of,  161. 
Oriental  Verde  marble,  214. 
Ornamental  brick,  defined,  260. 
Orthoclase,  properties  of,  8. 
Ortonville,  Minn.,  granite,  157. 
Owen  County,  Indiana,  191. 
Oxford,  Me.,  in. 

P. 

Pale  brick,  defined,  260. 
Paterson,  N.  J.,  168. 
Paving  brick,  defined,  260. 
Peach  Bottom  slate,  241. 
Peekskill,  N.  Y.,  granite,  137. 
Pegmatite,  defined,  18. 
Pen  Argyl,  Pa.,  241. 
Pennsylvania,  limestones  of,  189. 

marbles  of,  216. 

sandstones  of,  169. 

slates  of,  238. 

serpentine  of,  244. 
Penobscot,  Me.,  106. 
Penobscot  County,  Me.,  106. 
Penryn,  Calif.,  161. 
Peridotite,  characters  of,  23. 
Permanent  swelling  of  building  stone, 

69. 

Permeability  of  brick,  301. 
Petersburg,  Va.,  granite  described,  142. 
Phenix,  Mo.,  196. 
Phillipsburg,  N.  J.,  244. 
Phlogopite,  defined,  8. 
Phyllite,  defined,  31. 
Pickens  County,  Georgia,  218. 
Picton,  N.  Y.,  granite  described,  137. 
Pirsson,  L.  V.,  cited,  17. 
Pittsburg,  Pa.,  169. 
Pittsford,  Vt.,  202. 
Pittsford-Italian  marble,  213. 
Pittsford  Valley  marble,  213. 
Plagioclase  feldspars,  properties  of,  7. 
Plasticity  of  clay,  253. 
Plateau  white  marble,  213. 
Plattsburg,  N.  Y.,  216. 
Pleasant  River,   Me.,   use  of  granite 
from,  1 10. 


INDEX 


411 


Pleasantville,  N.  Y.,  215. 
Plutonic  rocks,  defined,  17. 
Pocahontas  marble,  223. 
Point  of  Rocks,  Md.,  216. 
Polish  of  building  stone,  40. 
Polk  County,  Ark.,  241. 
Pompeiian  brick,  defined,  260. 
Pompton,  N.  J.,  granite  described,  138. 
Porosity  of,  brick,  298. 

building  stone,  40. 

granite,  95. 
Porphyritic,  defined,  17. 

granite,  North  Carolina,  149. 
Port  Deposit,  Md.,  granite  described, 

141. 

Port  Deposit,  Md.,  100. 
Port  Henry,  N.  Y.,  244. 
Post,  defined,  226. 
Potsdam,  N.  Y.,  167. 
Potsdam  sandstone,  Mich.,  174. 

Wisconsin,  174,  175. 
Pownal,  Me.,  in. 
Pressed  brick,  defined,  260. 

requisite  qualities  of,  314. 
Princeton,  N.  J.,  168. 
Purdue,  A.  H.,  cited,  233. 
Pyrite,  as  coloring  agent,  in  building 
stone,  39. 

effect  of,  on  building  stone,  12. 

in  building  stone,  82. 

in  limestones,  181. 

in  marble,  198. 

in  slate,  226. 

properties  of,  12. 
Pyroxene,  properties  of,  9. 
Pyroxenite,  characters  of,  23. 

Q. 

Quarry  tile,  360. 
Quarry  water,  86. 

effect  of,  44. 

in  building  stone,  44. 
Quartz,  in  marbles,  198. 

in  slates,  226. 

properties  of,  7. 
Quartzite,  characters  of,  30. 

defined,  166. 


Quartzites,  distribution  of,  166. 
Quincy,  Mass.,  granite  described,  105, 
120,  125. 


R. 

Raleigh,  N.  C.,  granite  described,  149. 
Randolph,  Vt.,  116. 
Raymond,  Calif.,  161. 
Redbeach,  Me.,  in. 

granite  described,  109. 
Red  Beds,   Colorado,  sandstone  from, 

177. 

Redstone  granite,  N.  H.,  described,  112. 
Repressing  brick,  276. 
Rhode  Island,  granites  of,  described,  128. 
Rhyolite  of  Colorado,  160. 
Ribbons  in  slate,  defined,  226. 
Richmond,  Va.,  granite  described,  142. 
Ridge  tile,  361. 
Ries,  H.,  cited,  253. 
Rift,  96. 

Ridgefield,  N.  J.,  168. 
Rion,  S.  C.,  granite  described,  153. 
Riverside,  Calif.,  161. 
Riverside  County,  Calif.,  161. 
Rochester,  N.  Y.,  167,  189. 
Rochester,  Vt.,  116. 
Rock  face  brick,  defined,  260. 
Rocklin,  Calif.,  161. 
Rockmart,  Ga.,  241. 
Rockport,    Mass.,    granite    described, 

IOO,  1 2O. 

Rocks,  classification  of,  12. 

definition  of,  12. 

igneous,  defined,  12. 

plutonic,  defined,  17. 

volcanic,  defined,  17. 
Rockville,  Minn.,  100. 
Rockwood  County,  Ala.,  190. 
Rocky  Butte,  Ore.,  161. 
Roman  tile  (brick),  defined,  260. 

(roofing),  defined,  350. 
Roofing  tile,  absorption  of,  355. 

glazing,  value  of,  356. 

kinds  defined,  349. 

manufacture  of,  352. 

materials  used,  352. 


412 


INDEX 


Roofing  tile,  porosity  of,  352. 

requisite  characters,  359. 

special  shapes,  360. 

testing  of,  359. 
Rosaro  marble,  214. 
Rosiwal,  cited,  37. 

Rowan    County,    N.    C.,    granite    de- 
scribed, 149. 
Roxbury,  Vt.,  244. 
Royal  Blue  marble,  213. 
Royal  Red  marble,  214. 
Royal  Washington  serpentine,  249. 
Rubio  marble,  214. 
Run,  denned,  96. 
Ryegate,  Vt.,  116. 

S. 

Sainte  Genevieve,  Mo.,  196. 
Salida,  Colo.,  160. 
Salisbury,  N.  C.,  149. 
Salmon  brick,  defined,  263. 
Sandstones,  absorption  of,  163. 

analyses  of,  164. 

argillaceous,  defined,  29. 

arkose,  defined,  29. 

calcareous,  defined,  165. 

characters  of,  29. 

ferruginous,  defined,  166. 

micaceous,  29. 

as  building  stones,  162. 

cement  of,  162. 

color  of,  163. 

crushing  strength  of,  163. 

distribution  of,  166. 

fire  resistance  of,  165. 

hardness  of,  162. 
Sandstones  of,  Alabama,  170. 

Arkansas,  176. 

Atlantic  States,  167. 

California,  177. 

Central  States,  170. 

Colorado,  176. 

Connecticut,  166. 

Illinois,  174. 

Indiana,  173. 

Maryland,  169. 

Massachusetts,  166. 


Sandstones  of,  Michigan,  174. 

Minnesota,  175. 

Missouri,  176. 

Montana,  176. 

New  England  States,  166. 

New  Jersey,  168. 

New  York,  167. 

Ohio,  170. 

Pennsylvania,  169. 

Virginia,  170. 

Washington,  177. 

Western  States,  176. 

West  Virginia,  170. 

Wisconsin,  174. 

texture  of,  162. 

varieties  of,  165. 

weathering  of,  165. 
Sanitary  ware,  388. 

manufacture  of,  388. 

properties  of,  388. 

raw  materials  used,  388. 
San  Jose,  Calif.,  177. 
Sap,  in  stone  quarries,  87. 
Schist,  defined,  31. 

varieties  of,  31. 
Scove  kilns,  279. 
Sculping  of  slate,  229. 
Scumming  of  brick,  312. 
Scum  on  terra  cotta,  328. 
Searsport,  Me.,  in. 
Sedgwick,  Me.,  in. 
Semi-dry-press-process,  275. 
Seneca  Creek,  Md.,  169. 
Seneca  Red-stone,  Maryland,  169. 
Sericite,  defined,  8. 
Serpentine,  as  building  stone,  243. 

distribution  in  United  States,  243. 

mineral  impurities  of,  243. 
Serpentine  of,  California,  249. 

Georgia,  249. 

Massachusetts,  244. 

Maryland,  249. 

New  Jersey,  244. 

New  York,  244. 

Pennsylvania,  244. 

Vermont,  244. 

Washington,  249. 
Serpentine,  properties  of,  n. 


INDEX 


413 


Sewer  blocks,  385. 
Sewer  brick,  defined,  263. 
Sewer  pipe,  dimensions  of,  373. 

manufacture  of,  372. 

raw  materials  used,  372. 

requisite  qualities,  374. 

specifications  of,  377. 
Shakes,  defined,  96. 
Shale,  characters  of,  29. 
Shattuck  Mountain,  Me.,  no. 
Sheets,  defined,  96. 
Shelby  County,  Ala.,  190. 
Shenandoah  limestone,  Maryland,  190. 
Shingle  tile,  defined,  349. 
Shrinkage  of  clay,  254. 
Slate,  characters  of,  30. 

quarrying,  236. 
Slatedale,  Pa.,  241. 
Slates,  classification  of,  225. 

distribution  in  United  States,  236. 

for  building  purposes,  225. 
Slates  of,  Arkansas,  241. 

Georgia,  241. 

California,  242. 

Maine,  237. 

Maryland,  241. 

New  Jersey,  238. 

New  York,  238. 

Pennsylvania,  238. 

Vermont,  237. 

Virginia,  241. 

West  Virginia,  241. 
Slate,  properties  of,  226. 

price  of,  235. 

properties  of,  229. 

tests  of,  233. 

Slatington,  Pa.,  238,  241. 
Slip  cleavage  in  slate,  defined,  226. 
Slop  brick,  defined,  263. 
Snowflake  granite,  N.  H.,  113. 
Soapstone,  defined,  n. 
Soft-mud  bricks,  properties  of,  266. 
Soft-mud  process,  265. 
Soft-vein  slate,  Pennsylvania,  238. 
Solid-porcelain  sanitary  ware,  388. 
Soluble  salts,  in  brick,  312. 

in  building  stone,  39. 

in  terra  cotta,  328. 


Sonorousness  of  slate,  229. 
South  Berwick,  Me.,  in. 
South  Brookville,  Me.,  no. 
South  Carolina,  granites  of,  150. 
South  Dover,  N.  Y.,  215. 
Southern  marble,  218. 
South  Thomas  ton,  Me.,  no. 
Sparta,  Ga.,  granite  described,  154. 
Specifications,  for  sewer  pipe,  377. 

Iowa,  for  sewer  pipe,  379. 
Specific  gravity  of,  brick,  309. 

building  stone,  40. 

granites,  94. 

slate,  230. 

Spruce  Head,  Me.,  in. 
St.  Augustine,  Fla.,  181,  191. 
St.  Clair  County,  Ala.,  190. 
St.  Clair  County,  111.,  174. 
St.  Cloud,  Minn.,  granite,  100,  157. 
St.  George,  Me.,  111. 
St.  Louis,  Mo.,  196. 

St.  Peter's  sandstone,  Wisconsin,  174. 
St.  Stephen's  limestone,  Alabama,  191. 
Statuary  marble,  213. 
Steatite,  properties  of,  11. 
Stevens  County,  Wash.,  249. 
Stiff -mud  brick,  properties  of,  275. 
Stiff -mud  process,  269. 
S-tile,  defined,  350. 
Stockton,  N.  J.,  168. 
Stone     Mountain,     Ga.,     granite     de- 
scribed, 155. 
Stonington,  Me.,  uses  of  granite  from, 

1 10. 

Stony  Creek,  Conn.,  granite  described, 

131- 

Stout,  Colo.,  177. 
Stratification  (see  Bedding),  32. 
Strength  of  slate,  230. 
Stratified  rocks,  defined,  24. 
Structural  features  of  quarries,  31. 
Sturgeon  Bay,  Wis.,  195. 
Sullivan,  Me.,  in. 
Sulphur,  effect  on  clay,  257. 
Sulphuric  acid  gas,  effect  on  building 

stone,  74. 
Sulphurous  acid  gas,  effect  on  building 

stone,  74. 


INDEX 


Sussex  County,  N.  J.,  168,  189. 
Sutherland  Falls,  marble,  208. 
Swans  Island,  Me.,  no. 
Swanton,  Vt.,  202,  214. 
Swanville,  Me.,  in. 
Swain  County,  N.  C.,  217. 
Syenite,  characters  of,  23. 

Arkansas,  159. 

Missouri,  100. 

porphyry,  denned,  23. 
Sylacauga,  Ala.,  223. 


Talc,  properties  of,  u. 

Talladega  County,  Ala.,  122,  190. 

Tapestry  brick,  denned,  263. 

Taylor's  Mill,  Ala.,  223. 

Temecula,  Calif.,  161. 

Tenino  sandstone,  Washington,  177. 

Tennessee,  marbles  of,  218. 

Tensile  strength  of  clay,  255. 

Terra  cotta,  architectural,  denned,  320. 

fire-resisting  properties,  328. 

manufacture  of,  320. 

properties  of,  324. 

raw  materials  used,  320. 

scum,  328. 

testing  of,  324. 

lumber,  defined,  333. 
Testing  brick,  methods  used,  284. 
Tests  for  brick  scum,  313. 
Tests  of,  fire-proofing,  341. 

hollow  blocks,  340. 

roofing  tile,  359. 

sandstone,  164. 

sewer  pipe,  383. 

slate,  233,  234. 

Tests,  proposed,  for  sewer  pipe,  382. 
Texas,  granites  of,  160. 

limestones  of,  197. 

Maryland,  216. 
Texas  Creek,  Colo.,  160. 
Texture  of,  building  stone,  36. 

sandstones,  162. 
Topsham,  Vt.,  116. 
Toughness  of  slate,  230. 
Toula,  cited,  37. 
Tournaire,  cited,  51. 


Tower  tile,  361. 

Transverse  strength  of  building  stone, 
Si- 

effect  of  heat  on,  53. 
Transverse  test  of  brick,  294. 
Trap  Rock,  New  Jersey,  138. 

in  Virginia,  145. 
Travertine,  defined,  30,  184. 

worked  in  Italy,  184. 
Tremolite,  in  marble,  198. 

properties  of,  9. 
Trempeleau,  Wis.,  195. 
Trenton  limestone,  Ala.,  190. 

Missouri,  196. 

New  York,  189. 

Wisconsin,  192,  195. 
Troy,  N.  H.,  granite  described,  111,112. 
True  Blue  marble,  213. 
Tuckahoe,  N.  Y.,  215. 
Tufa,  calcareous,  defined,  30. 
Tuff,  defined,  17. 
Tuscaloosa,  Ala.,  170. 

U. 

Unakite,  in  Virginia,  145. 


V. 

Valley  tile,  360. 

Verdolite,  244. 

Verdoso  marble,  214. 

Verdura  marble,  214. 

Vermont,  granites  described,  116. 

marbles,  varieties  of,  207. 

marbles  of,  202. 

serpentine  of,  244. 

slate  of,  237. 
Veins  in  slate,  226. 
Victorville,  Calif.,  249. 
Vinalhaven,    Me.,    granite    described, 

109,  no,  in. 
Virginia,  granites  of,  142. 

limestones  of,  190. 

marbles  of,  217. 

sandstones  of,  170. 

slates  of,  241. 
Vitreous  sanitary  ware,  388. 


INDEX 


415 


Volcanic  ash,  as  a  building  stone,  93. 

Montana,  160. 
Volcanic  locks,  denned,  17. 

W. 

Waldoboro,  Me.,  in. 
Wall  tile,  manufacture,  363. 

tests  of,  369. 
Wallingford,  Vt.,  202. 
Warren,  Wis.,  granite  described,  156. 
Warren  County,  Ind.,  173. 

New  Jersey,  168,  189. 
Warrensburg,  Mo.,  176. 
Warsaw  Bluestone,  N.  Y.,  168. 
Washburn,  Wis.y  175. 
Washington  County,  Me.,  106. 

New  York,  237,  238. 
Washington  monument,  marble  in,  216. 
Washington,  sandstones  of,  177. 

serpentine  of,  249. 
Watchung,  N.  J.,  168. 
Water,  effect  on  building  stone,  81. 
Waterford  township,  Conn.,  granite  de- 
scribed, 131. 

Watson,  T.  L.,  cited,  50,  146. 
Waupaca,  Wis.,  granite  described,  156. 
Wausau,  Wis.,  granite  described,  157. 
Wauwatosa,  Wis.,  195. 
Weathering  of,  building  stone,  75. 

limestones,  181. 

marbles,  201. 

sandstones,  165. 
Weisner  sandstone,  Ala.,  170. 
Welch's  Spur,  Mont.,  160. 
Wells,  Me.,  no. 


West  Chester,  Pa.,  244. 

Westerly,  R.  L,  granite  described,  100, 

105,  128. 

West  Monson,  Me.,  237. 
West  Rutland,  Vt.,  202,  207. 
West  Virginia,  limestones  of,  190. 
sandstones  of,  170. 
slates  of,  241. 
Wheeler,  H.  A.,  cited,  352. 
Whitefield,  Me.,  in. 
Whitehall,  N.  Y.,  238. 
Wichita  Mountains,  Oklahoma,  granites 

described,  159. 
Wilburtha,  N.  J.,  168. 
Will  County,  111.,  191. 
Williams,  J.  F.,  cited,  37. 
Wilson  County,  N.  C.,  146. 
Windsor,  Vt.,  granite  described,  116. 
Wisconsin,  granites  of,  155. 
limestones  of,  192. 
sandstones  of,  174. 
Wise,  N.  C.,  granite  described,  149. 
Woodbury,     Vt.,     granite     described, 

119. 

Woodbury,  Vt.,  116. 
Woodstock,  Me.,  in. 
Woodstock,    Md.,    granite    described, 

141. 

Woolson,  I.  H.,  cited,  303,  346. 
Worthy,  Ind.,  174. 

Wyoming  Valley  stone,  Pennsylvania, 
169. 

Y. 

York  County,  Me.,  106. 
Yule  Creek,  Colo.,  223. 


~ 


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JUL   I 


1935 


MAY  261947 


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UNIVERSITY  OF  CALIFORNIA  LIBRARY 


